The Impossible Flight

For the first time, two intrepid pilots fly a solar-powered airplane around the world. Airing January 31, 2018 at 9 pm on PBS Aired January 31, 2018 on PBS

Program Description

On March 9, 2015, Solar Impulse II took off from Abu Dhabi on one of the greatest aviation adventures of our time: the first solar-powered flight around the world. Together with a team of brilliant engineers, two visionary pilots—Bertrand Piccard and André Borschberg—designed and built Solar Impulse from scratch, even though top airplane manufacturers told them it would be “impossible to control.” To pull it off, they had to re-invent everything, from innovative solar cells and batteries to massive carbon-fiber wings. Despite all their efforts, the performance of the plane was balanced on a knife-edge, demanding near-perfect weather conditions and hour after hour of vigilant, skillful piloting. The longest nonstop leg, from Japan to Hawaii, lasted five days and set a new world solo flight record. NOVA captures an insider’s view of the Solar Impulse pilots and ground team as they experience moments of hair-raising crisis, remarkable endurance, and ingenious problem-solving.


The Impossible Flight

PBS Airdate: January 31, 2018

NARRATOR: A mission like no other: a plane, powered only by the sun, set to fly around the world without a drop of fuel.

BERTRAND PICCARD (Pilot, Co-Founder Solar Impulse): What we do in the air, we can do on the ground. And this is our message.

NARRATOR: This journey will push the limits of technology.

NILS RYSER (Head of Ground Operations): It's made of fabric, it's made of carbon; and you can break it with your finger.

NARRATOR: It will test the endurance of its pilots.

MICHAEL ANGER (Lead Mission Engineer): And something wrong, just one thing, they could die. And you carry that for your, for the rest of your life.

NARRATOR: Flying solo day and night,…  

ANDRÉ BORSCHBERG (Pilot, Co-Founder Solar Impulse): We never flew over the ocean five nights in a row. That's the main challenge.

BERTRAND PICCARD: …switching on the solar generators.

NARRATOR: …they will risk their lives…

WIM DE TROYER (Meteorologist): There's bad weather coming in and then thunderstorms. And afterwards it's turning northwest.

RAYMOND CLERC (Mission Director): Either we divert, or we take a big risk.

NARRATOR: …to realize a dream for our planet.

BERTRAND PICCARD: The decision we take goes far beyond the flight itself.

NARRATOR: The Impossible Flight, right now, on NOVA.

To fly, fueled only by the power of the sun: it's an audacious idea that gave rise to an airplane unlike any other ever built. Now embarking on a revolutionary and risky mission…

THOMAS SEILER (Head of Energy & Propulsion): The risk is really high.

MICHAEL ANGER: I don't want to gamble with a pilot in the ocean.

BERTRAND PICCARD: A lot of people can be a little bit afraid, scared, by the, by the unknown in which we are jumping.

NARRATOR: …a perilous journey: 26,000 miles around the world without a drop of fuel.

PETER FREI (Head of Safety Review Board): I think it's very dangerous. You know, we never have the story of those who got killed.

ANDRÉ BORSCHBERG: We have to do it to demonstrate it works. So, someone has to do it first. Someone has to try.

NARRATOR: The zero-fuel flight begins in Abu Dhabi, in the United Arab Emirates, where the sun's energy is in abundance nearly every day of the year.

BERTRAND PICCARD: To have an airplane that could fly forever without fuel, no noise, no pollution; that was the dream from the beginning.

We can move it a little bit. It's a little bit, just a little bit.

NARRATOR: It was a dream that aviation experts quickly dismissed. A solar plane capable of carrying a person around the world would have to be too big, too light, and likely impossible to control.

BERTRAND PICCARD: There are moments where you have to take some risks, if you want to achieve something that has never been done. Otherwise, we stay in the armchair, and we wait until we're old and we do nothing.

RADIO NEWS CLIP: We're in the early hours of the morning here. The Solar Impulse 2 is ready to embark on its ambitious round the world journey.

NARRATOR: After weeks of flight tests over Abu Dhabi, the airplane, known as Solar Impulse, prepares for takeoff. Over 3,000 miles away, flight operations are run from a command center in Monaco.

MICHAEL ANGER: Okay, André, everything is ready. We still wait for the final go from the S.R.B.

NARRATOR: The project is the brainchild of Bertrand Piccard, psychiatrist, adventurer and heir to a family legacy of scientific exploration.

BERTRAND PICCARD: In 1969, I was 11, and I saw Apollo 11 taking off to the moon, and I said, “I want to have that type of life.”

Sixteen years I've been dreaming of that: to start a flight around the world with no fuel.

There are doubts all the time. When you're doing something that nobody has done before, the doubts are important. If you are on a straight line with your beliefs, you never succeed in something new.

CAP COM: Solar Impulse from Solar Ground, confirm you get the clearance.

MICHAEL ANGER: Okay, solar generator looks good. Continue with engines then. Have a good flight, André. Let's start the adventure.

ANDRÉ BORSCHBERG: Okay, finally. It's the magic, magic moment.

CAP COM: Main wheel liftoff.


(Translated from French) Have a good flight, André, my friend, my solar brother.

ANDRÉ BORSCHBERG: (Translated from French) Thank you, Bertrand. I'll be thinking of you and the entire team every minute.

BERTRAND PICCARD: (Translated from French) Incredible! Incredible! A morning as long as the last twelve years.

ANDRÉ BORSCHBERG: Thank you very much.

Currently, altitude 5,300 feet.

NARRATOR: To help make his dream a reality, Bertrand turned to André Borschberg, a man known for pushing boundaries, both as a fighter pilot in the Swiss air force and an engineer with a graduate degree from M.I.T.

ANDRÉ BORSCHBERG: The airplane was considered to be impossible to be built and flown. The challenge is how? I mean, to make something like this, eh? Here is an airplane we designed, we, we dreamt about. It's a big part of, part of me.

RADIO NEWS CLIP: It is really a phenomenal sight but crazy to believe that it is just the sun powering that plane here.

RADIO NEWS CLIP: Their dream is to show a way forward without fossil fuels and spread a message about the need to fight climate change.

NARRATOR: They are planning on about 12 flight legs. With only one seat in the plane, the pilots will have to take turns in the cockpit. The most difficult will be the flights over the world's two largest oceans, lasting anywhere from three to five days.

At an average speed of just 45 miles an hour, the 26,000-mile trip will be long and full of uncertainty.

BERTRAND PICCARD: Five months now, the plane starting this way. If everything goes well, comes back this way in July.

It is so much more difficult to use these clean technologies in the air than to use them on the ground. So if it works in the air, I really hope people will understand that they can replace all these old, polluting old stuff by new, clean technologies. What we do in the air we can do on the ground. And this is our message.

ANDRÉ BORSCHBERG: When you fly with the sun as the only source of energy, that's a completely different world, a different feeling.

NARRATOR: The revolutionary plane is powered by over 17,000 solar cells that collect and transform the sun's rays into electricity. That energy is distributed to four 17-horsepower engines, each with the daily power output of a small motor scooter. Any spare energy is stored in four lithium polymer batteries, which enable the plane to fly at night or under cloud cover.

The dilemma was how to build something big enough to collect maximum sunlight, but light enough to run on as little energy as possible. The tradeoff was instability in anything but perfect weather.

The plane is fragile and vulnerable to the elements.

LUC TRULLEMANS (Lead Meteorologist): Hello, André. Below you, you have a small thermal inversion, and below this thermal inversion, you have all this dust and haze.

NARRATOR: At mission control, in Monaco, a team of meteorologists, engineers, and mission planners—many of them also highly-trained pilots—monitors an array of instrumentation and weather models during flight.

CAP COM: You can put some more power,…

NARRATOR: Lead meteorologist Luc Trullemans has guided long-range aviation and ballooning expeditions across the globe, but this mission presents a unique challenge.

LUC TRULLEMANS: This aircraft is so very light, so fragile, trying to find the places where he can fly is not so easy. When you have a downdraft or updrafts, this aircraft can break in two. Rain, humidity and turbulence, forget it; only sun and quiet weather and tailwinds.

NARRATOR: On this flight, they must steer clear of dust storms and turbulence caused by heat rising off the desert.

Each flight leg will have its own difficulties, like avoiding thunderstorms and crosswinds, which could blow the plane off course.

MICHAEL ANGER: We are excited, but there's a lot of fear, as well. I think the overall round the world flight you can compare to an Apollo mission. If you do, do something wrong, just one thing, they could die. And you carry that for your, for the rest of your life.

NARRATOR: The most dangerous part of every flight is the landing, where the fragile wings are that much closer to the ground.

This pit stop in Muscat, Oman is just long enough to clean the dust off the solar wings before the next leg to Ahmedabad, India.

The team back in Monaco plans on using high altitude winds to push the plane away from incoming clouds. These thin and wispy cirrus clouds could block a critical amount of sunlight.

For this 15-hour flight across the Arabian Sea, Bertrand will take the controls.

BERTRAND PICCARD: Microphone and headphone and the cuffs. When it starts to vibrate on your arm, and this is to alert the pilot if the bank is too, too high.

NARRATOR: With no heat in the cockpit, the pilots must wear heated boots and a sub-zero-rated parka. Inside the cockpit, temperatures will range from minus-4 degrees Fahrenheit to 95 degrees when they descend during the summer heat.

Solar Impulse's ground crew readies the plane to take off before sunrise, to avoid turbulence and stay one step ahead of the clouds.

BERTRAND PICCARD: When I was a child, I was afraid to climb in the tree. Fear is there. Either you have no fear at all, which means you're completely crazy, or you have some fear, which means that you are not a daredevil. It might not go well, but the only way to know is to try.

CAPCOM: Solar Impulse, solar control…

NARRATOR: Bertrand's passion for exploration has deep family roots.

BERTRAND PICCARD: What interests me the most is not to break a record, but to do a first. My father and my grandfather were the first to the bottom of the ocean, showing there was life in the deepest trenches; the first in the stratosphere, to see with his own eyes the curvature of the earth. When you do the first, you establish the first benchmark, and from there, a lot of new things can come out.

I flew 20 days nonstop with a balloon. Every day, I was afraid to fall short of fuel, and it was almost a failure. We just succeeded because we had two hours of margin with the propane after 20 days. And that's when I made the promise that I would fly around the world with no fuel.

NARRATOR: Flying balloons is one thing, flying an experimental solar-powered plane is quite another.

Bertrand only got his pilot's license in his 50s, and he couldn't have picked a more difficult airplane to learn how to fly. Because it is so big and light, it's particularly unwieldy; banking more than 10 degrees will throw the plane into a tailspin. And because it's underpowered, there's no quick way out of danger.

After 12 hours in flight, as he approaches the airport in Ahmedabad, Bertrand runs into trouble.

BERTRAND PICCARD: I have oscillations like hell. It's crazy. I never saw Solar Impulse be so unstable.

CHRISTOPHE BÉESAU (Simulation Expert): You said the aircraft is unstable, and I don't see any turbulence at all.

BERTRAND PICCARD: It's unstable on the heading. Did you see what happened just now?

CHRISTOPHE BÉESAU: Yeah, I see it. It's a heading change of 15 degrees, without any problem from outside. From what I see on the data, it looks just perfectly calm.

NARRATOR: Alarmed and puzzled by what's causing the problem, mission control in Monaco sets up an emergency call with André, who is already at the Ahmedabad airport.

CHRISTOPHE BÉESAU: There he is. André, hello. Bertrand started to say the aircraft is unstable, and the autopilot cannot be connected and had a few times sideslips of up to 15 degrees, and he said it's…


CHRISTOPHE BÉESAU: Fifteen, 1-5 degrees, and he said it's really hard to control.

ANDRÉ BORSCHBERG: Should we start looking for a helicopter, just in case? First of all, I think he should be ready to jump, right? Yes?

MICHAEL ANGER: Here, we are looking for a bailout area in the area he's flying for the moment.

PETER FREI: If it's a pilot problem, you know, pilot-induced oscillation, I think we should take time, do everything very calm.

NARRATOR: Unsure whether it's a problem with the plane or pilot error, the mission team performs a series of handling checks before landing.

BERTRAND PICCARD: No, now it's completely stable…


BERTRAND PICCARD: …because now I can keep the heading without the autopilot.

CHRISTOPHE BÉESAU: Okay, Bertrand. Then the next thing I like you to extend the outriggers and then slowly go down.

ANDRÉ BORSCHBERG: (Translated from French) It made me a little frightened there.

BERTRAND PICCARD: (Translated from French) Oh, please.

ANDRÉ BORSCHBERG: (Translated from French) We're always worried.

MEMBER OF THE PRESS: How was the flight?

BERTRAND PICCARD: It was fantastic flight, fantastic flight.

MEMBER OF THE PRESS: Any challenges or difficulties?

ANDRÉ BORSCHBERG: Always challenges with an experimental airplane. You always discover, you always learn.

MEMBER OF THE PRESS: The bigger challenge lies ahead: you have to cross the Pacific. Are you looking up to that challenge?

BERTRAND PICCARD: Ah, yes, well it's going to be really impressive, I tell you, to cross the Pacific, to cross the Atlantic.

ANDRÉ BORSCHBERG: It's not done yet.

BERTRAND PICCARD: You can imagine that?

ANDRÉ BORSCHBERG: It's not done yet.

YOUNG GIRL LOOKING AT SOLAR IMPULSE: This plane has the capacity to take the rays of the sun…

WOMAN LOOKING AT SOLAR IMPULSE: I got the chance to see this plane, and it's a once in a lifetime moment.

NARRATOR: After each flight, the plane must be meticulously cleaned and inspected. Even minor damage could pose a serious threat.

ROBERT FRAEFEL (Head of Airplane Development): I think it's enough.

CREW MEMBER: I think we had some rust in the needle…

ROBBI FRAEFEL: We had a little delamination on one of the solar panels.

CREW MEMBER: No, don't push too much.

ROBBI FRAEFEL: No, it's perfect. This white spot can overheat one of these individual cells. If one cell gets damaged, like with the light bulbs in a Christmas tree, you break down all the others as well.

NARRATOR: To build the “impossible plane” required some unconventional thinking. André pulled together a diverse team of engineers from aerospace, Formula One racing, even elevator manufacturing.

SÉBASTIEN DEMONT (Lead Electrical Engineer): Lot of time where we thought it would be impossible to finish the project: it's too crazy, it's too hard.

NARRATOR: Over 13 years of design and testing, weight was the archenemy for lead designer Peter Frei.

PETER FREI: I just knew from the beginning that it must be a superlight aircraft. Thirteen years ago, the thrill: “Wow, is it possible? Is it not possible?” And it was an up and down, you know, fighting, success, failures.

NARRATOR: What they ultimately came up with was a plane with a structure that's ten times lighter than the best gliders.

More than 17,000 solar cells, each as thin as a human hair, make up the top surface of the wing and fuselage. These lightweight flexible cells, store nearly 50 percent more sunlight than solar panels on average homes.

They built a skeletal structure that was largely hollow—like the bones of a bird—using carbon fiber three times lighter than paper.

But there was one major design hurdle they'd have to overcome.

ROBBI FRAEFEL: To know exactly the capacity of a battery, it's a really difficult story, not only for us, for everybody who tries to implement batteries in a car or in a bicycle or something.

NARRATOR: To store enough energy to keep the plane aloft through the night, they calculated that the four batteries would weigh nearly 1,500 pounds, a quarter of the plane's total weight. So every other component onboard had to be lightweight and extremely energy efficient.

ANDRÉ BORSCHBERG: The efficiency of the electric motors, we have 97 percent; only three percent of losses. And if you compare this with a piston engine, the efficiency of the system is between 30, 40, maybe 45 percent.

The engineers, the team has done an incredible job. I mean, that's a Swiss watch of a size of a 747.

NARRATOR: With far fewer moving parts than an internal combustion engine, the four electric engines lose very little energy through heat and generate almost no friction. Like a smart grid, the network of solar cells connects to the four motors and batteries sitting behind the propellers. The cells capture the sun's energy and convert it into electricity, which flows through the grid to power the engines. Any excess charges the batteries.

PETER FREI: We charge the batteries in nine to 10 hours, and we extract the energy in eight to nine hours. So this is a very low rate, and that's why we have losses in the region of one to two percent.

NARRATOR: But with the power output only slightly more than the Wright brothers' first plane, the aircraft teeters right on the edge of flight. Failure is a real possibility, especially on the multi-day solo flights over the oceans. And both pilots had to train for the worst-case scenario.

ANDRÉ BORSCHBERG: We never flew over the ocean five nights in a row. That's the main challenge. The last measure we can take is to bail out, but, of course, you want to bail out when you really have to bail out.

If you do this mission you have to be on the positive side, or you will never do it.

Building the airplane, I think I'm realizing a dream I had when I was really a little boy, thinking about these pilots who were discovering aviation, these pioneers. I met Bertrand at the right moment with a great idea.

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I always have been a little bit rebellious against authority. I left home when I was quite young. What I learned as a fighter pilot, which was useful, I think you are trained to better appreciate the risk and come up with the right decision.

NARRATOR: But decisions are made on the ground as well as in the air. To find the best possible route around the world, the mission control team pours over computer models and global satellite data.

LUC TRULLEMANS: I am working on this since five years, so I was watching all the airports with less rain, less windy conditions, less cloudy conditions. That's the reason that we will fly around the world in a tropical area during the dry season.

NARRATOR: Their route follows a broad tropical band around the earth, between the monsoons to the south and cold storm fronts in the north.

After leapfrogging across India to Myanmar, the plan is to get to China in time to make their first ocean crossing in early summer, when the hours of sunlight are reaching their peak.

But no matter how much they map out beforehand, the pilots must be ready to change course at a moment's notice.

In places like Mandalay, in Myanmar, the problem is that a hangar big enough to house the plane isn't easy to come by. So, the team has to be self-sufficient. They came up with a waterproof, windproof mobile hanger that inflates like a giant bouncy castle. This 7,000-pound shelter takes the 20-person ground crew five hours to set up.

NILS RYSER: On the ground, this aircraft has a lot of weak points. It is big, it is light, and therefore, it is fragile. It's made of fabric, it's made of carbon; and you can break it with your finger.

NARRATOR: The five-day, solo Pacific flight will be the ultimate test, not just for the experimental airplane but also for the pilots. If successful, it would beat the existing world record in any plane by nearly two days.

In the lead up to the mission, the pilots spent three straight days crammed in a flight simulator. While doctors monitored their brainwaves and vital signs, they performed mental vigilance and stress tests. The long duration of the ocean flights is a concern for mission director and veteran pilot Raymond Clerc.

RAYMOND CLERC: Shut down engine Number 2 and, and wait.

This operation is really pushing the human performance to the limits. The airline pilots, they fly always two in the cockpit, you know? The normal flights, they last already 12 hours, and they can sleep during the flight. Our pilots, they don't have this chance.

NARRATOR: Because they'll be alone, the pilots can't risk falling into a deep sleep, which would make them too groggy to take over the controls in an emergency. So the pilots practice a resting technique used by the military and NASA: 20-minute catnaps throughout the day, adding up to around three hours of sleep, every 24 hours.

Now in Myanmar, it's nearly a month into their journey, and they are halfway across Asia. These shorter duration flights serve as the final test as they get closer to the first ocean crossing.

But first Solar Impulse's safety review board must make a final call on which pilot will fly the critical leg to Hawaii. Bertrand's difficulty flying at night on his first flight to India raises doubts about his readiness, during a mission control debrief meeting in Monaco.

PETER FREI: Bertrand, I really would like to have more details on this phase before landing in Ahmedabad. What happened there? Because, you know, we had really some stressed situation on the ground.

BERTRAND PICCARD: I made a mistake in flying the plane in an unstable way, and I really scared everybody, so, I was really, I was very embarrassed.

MARCUS BASIEN (Safety Review Board/Head of Flight Test): Not being prepared good enough, pilot condition must be better than what it was.

BERTRAND PICCARD: Now, of course I don't have the same reactions than a jet plane pilot.

CHRISTOPHE BÉESAU: No, which is not necessarily a bad thing.

NARRATOR: While in Myanmar, the safety review board ultimately decides that Bertrand needs more training before making an ocean crossing. André is chosen to pilot the dangerous flight to Hawaii.

BERTRAND PICCARD: (Translated from French) I don't want to get hung up on the Pacific flight, because it pisses me off that the Safety Review Board thinks I am not capable and has told me I have to show them I'm capable.

ANDRÉ BORSCHBERG: (Translated from French) Bertrand, the two qualities you need for this flight: one is obviously good piloting skills and the second is adaptability.

BERTRAND PICCARD: (Translated from French) We'll see at the end of the flight if the pilot's experience is the most important thing or if the experience of 35 days and nights in a hot air balloon is more fundamental.

(Translated from French) We don't know we'll see.

ANDRÉ BORSCHBERG: (Translated from French) The difficulty with the plane is that you can't sleep. In the balloon, you can sleep. The plane doesn't let your mind rest, that's the fundamental difference.

BERTRAND PICCARD: I was extremely disappointed not to make the Pacific. That was my dream from the beginning. I think I underestimated the difficulty to fly it. On this airplane, it's not like on a normal airplane. I have to be really more precise.

I initiated the project to fly in that airplane, but then, the same time, it's true, I'm not the best pilot. I'm the explorer who became a pilot. I had to learn to fly that airplane. And, and it's not easy for me.

ANDRÉ BORSCHBERG: This decision was extremely difficult for everybody, yeah? Especially when there are a lot of emotions and, and so much at stake. If I would do the Pacific, I knew that I had to prepare myself very well.

When I will be in this cockpit, there will be moments where it will be too intense. We will sleep, but for very short time, 20 minutes resting period.

Yoga, meditation, breathing, it's a way to reboot the system, which is start to be congested.

When you fly jet fighters, you have whatever power you need to go against the winds, to fly in turbulence, in bad weather. Here, it's just the other way around. This airplane is like a leaf pushed around by the wind. You have to make nature as a partner and not as an enemy. I think that's an attitude in life, in some ways, I discovered when flying this airplane.

NARRATOR: From Mandalay, Solar Impulse moves on to Chongqing, China, one of the largest and fastest growing cities in the world.

BERTRAND PICCARD: People say there is too much pollution, there is climate change, but it's not enough to complain about problems. We have to bring solutions. The same technologies that can make an airplane fly day and night with no fuel can be used to divide by two the emissions of CO2.

STUDENT LOOKING AT SOLAR IMPULSE: After seeing this, I think in my future, my future job, maybe I will do something like this. We have to think about our children, our grandchildren. This thing is for them.

BERTRAND PICCARD: With Solar Impulse we are only at the first phase. Our goal is not to transport passengers. Our goal is to transport a message.

With André, we've done six legs from Abu Dhabi to here. Now it's time to go to the next level, and it's the ocean. This is why Solar Impulse is built.

PHILLIPPE MANUEL (Deputy Flight Director): It's five days and five nights, solo flights over water. It's like going to the moon. Everything is under control, but you still have to go to the moon.

ANDRÉ BORSCHBERG: The challenge with the solar energy is to fly through the night. The energy of the airplane is the critical factor. During the day, we climb very high altitudes, we collect energy directly from the sun. And we use this altitude at the beginning of the night to slowly fly down. This saves the batteries. Minimum battery charge is, if everything goes on plan, is not more than 10 percent in the morning, at sunrise. It's about an hour. So there is not much margin, eh?

NARRATOR: To conserve energy, the wings are designed for maximum lift and to create a high glide ratio and low sink rate. If the engines were turned off at 28,000 feet, a jumbo jet would glide for 20 minutes, compared to four or five hours for Solar Impulse.

They had to thread the needle of aerodynamic design. The larger the wingspan, the more energy they capture, but the more unstable the plane is in choppy weather. But if the wingspan were just 10 percent smaller, they might not have enough energy to make it to sunrise.

CREW MEMBER: Everything okay, there?

ROBBI FRAEFEL: Okay, let's move forward.

SÉBASTIEN DEMONT: We are removing each gram that we can in this airplane, because each gram, of course, is consuming energy.

ANDRÉ BORSCHBERG: I did the most weight saving, because I lost four kilos during the last four months there. So, I did my contribution.

ROBBI FRAEFEL: We were never able to prove that the airplane can fly through the night, so far. And reducing weight is reducing risk.

CREW MEMBER: The lighter you are, the further you get.

ROBBI FRAEFEL: Who knows? I mean, maybe this is the minute which counts.

SÉBASTIEN DEMONT: Yeah, exactly.

LUC TRULLEMANS: The Pacific is the largest ocean on the earth. It's something that is always moving, developing, dying. Depressions, typhoons, it's like a soup.

NARRATOR: Since Solar Impulse must climb over 25,000 feet each day, the weather team has to forecast 16 different layers of wind, humidity and temperature.

WIM DE TROYER: The most difficult part of this Pacific flight to, to Hawaii is the crossing of a classical cold front that acts like, like a wall. Cloudiness that gives precipitation, so all things that you have to avoid. And we have to find a hole in that frontal system? Every day, we are looking for a hole, we're even dreaming about, about a hole.

NARRATOR: The hard part is that after three days, the reliability of their forecast drops below 70 percent.

WIM DE TROYER: Flying to Hawaii takes five, maybe six days. When you cross that front, you have to be sure about details, and five days ahead, it's difficult, it's difficult to say.

RADIO NEWS CLIP: Weather is posing a big problem for the Solar Impulse plane.

RADIO NEWS CLIP: The Solar Impulse has been grounded in China due to bad weather brewing over the Pacific Ocean.

SÉBASTIEN DEMONT: If it happens that you have bad weather, pilot tired and technology problem, there it's the biggest risk we have. You dream of it almost all night, because if there is a failure, there is a person in there.

ROBBI FRAEFEL: It's not only that we have the risk of losing the pilot, but it will also change the life of every engineer, which André maybe doesn't realize all the time.

ANDRÉ BORSCHBERG: Yes, I can hear you loud and clear. Yes.

How much? How much?

The closer we get, now, more intense it is. The first time I will fall asleep will be over the ocean. We all know that falling asleep when you are stressed, not easy, eh?

Of course, if I end up in the water, it will be a shame, but I'm ready for a lot of things to happen. There will be moment of actions; there will be moment of reflection. I hope not moment of regret. This inner voyage is really what I'm looking for, to go through these different experiences. This is the gift of all that.

BERTRAND PICCARD: You put, “Breaking news: takeoff tonight.” Starting to be exciting.

VINCENT COLEGRAVE (Chief Digital and Government Affiars): Finally.

MICHAEL ANGER: I'm getting emotional a little bit, sorry. I'm so happy.

ANDRÉ BORSCHBERG: Do we have a good corridor to get to the hole, or we do not have a good corridor to get to the hole?

MICHAEL ANGER: The hole's still there, yes, it is there. It's more or less confirmed.

NARRATOR: But a few hours later, there is a change.

MICHAEL ANGER: Takeoff, we have cirrocumulus, which are new. They were not seen before.

NARRATOR: High-altitude clouds that block sunlight have moved in around Nanjing and will reduce their energy right from the start.

MICHAEL ANGER: That front, that hole is moving a little bit to the east, I think, yeah?

NARRATOR: On top of that, tailwinds are decreasing. The flight is getting longer, and they'll have to cross the cold front later in their journey, when the forecast is less certain.

ANDRÉ BORSCHBERG: What's the flight time?

CHRISTOPHE BÉESAU: Flight time is six days and a …


MICHAEL ANGER: Having a seventh day, it's not, not acceptable for me. If it's five and a half, okay, on the edge. But if it's six and something, it's…

ANDRÉ BORSCHBERG: I mean, if I look at everything now, I have the impression we are pushing a little bit too far there.

RAYMOND CLERC: We are at seven hours from departure.

MICHAEL ANGER: It's tight there, it's tight. And uncertainty due to energy.

ANDRÉ BORSCHBERG: We have too many issues, that's the problem. We have too many issues now.


NARRATOR: After working around the clock for days on end, it's a huge blow to the team. They are exhausted, but they must keep going.

RAYMOND CLERC: The guys fighting each other because they are nervous, they are under tension, they are tired.

BERTRAND PICCARD: If it's the window of the year, we just have to do it.

RAYMOND CLERC: We're not going to do it for tomorrow. I'm sorry, yeah, but I think we'll not have a solution for tomorrow evening.

MICHAEL ANGER: The time to prepare a distance of such a huge window, the weather maps and so on, it's not done in three hours.

LUC TRULLEMANS: He's tired, he's tired. They are tired.

WIM DE TROYER: Don't forget that the distance from Nanjing to Hawaii is almost two times Europe, and then you're asking us, what's the clouds going to be like in Poland and in Greece and in Ukraine. In three hours? I mean …

LUC TRULLEMANS: With two people!

WIM DE TROYER: I like my job. I like my job.


WIM DE TROYER: But it was hell.

RAYMOND CLERC: I would prefer that we take some rest, and tomorrow morning we start to fight for the next one.

BERTRAND PICCARD: Fresh and rested.

It worries me very much. If you look in the history of exploration, most of the big attempts have failed several times before the success.

NARRATOR: While the flight team waits in Nanjing, temperatures inside the hangar reach around 100 degrees.

Lead engineer Robbi Fraefel is using portable air conditioners and jerry-rigged tubing to pump cold air into the battery compartments.

Inside each of the four custom-built lithium polymer batteries are 70 individual cells, laid out like squares of a chocolate bar, where the chemical reactions take place. The cells are similar to those used in mobile phones, but their chemistry has been optimized to boost performance.

The challenge with batteries is that they rely on chemical reactions, which are sensitive to temperature.

ROBBI FRAEFEL: A battery likes to stay always in the same temperature, same pressure, and if we change both all the time, it's not good for the battery. With every 10 degrees higher temperature, the aging is about double. So, it makes quite a difference. Only the Pacific flight will show the truth.

NARRATOR: Working day- and nightshifts at mission control, they struggle to find a way through the front, running hundreds of computer simulations to come up with the best course.

CHRISTOPHE BÉESAU: In the simulation, you play with the aircraft, you play with the possibilities of flight, like if it was a game.

NARRATOR: There are many variables to take into account: weather, air traffic restrictions and energy demands of both the plane and the pilot.

CHRISTOPHE BÉESAU: From one simulation to another one, you see things are moving, so it's not good.

NARRATOR: After a month of striking out, the weather team finally sees their chance. There's a weak cold front five days out, but the team is confident that the plane can cross it.

WIM DE TROYER: Is this what you were dreaming of? We will have a nice corridor behind this system onto the ocean, three, even four days flying in sunshine.


ANDRÉ BORSCHBERG: Now, it's the moment of truth, the first time that this airplane will fly with such a long time.

NILS RYSER: Okay, we move.

RAYMOND CLERC: For the time being, looking good.

NARRATOR: With nothing but open ocean ahead of him, André will face 120 hours alone in the cockpit, longer than any human has sustained before.

YASEMIN BORSCHBERG (André Borschberg's Wife): He's doing this really with a lot of his heart and all his being. I don't think anything else matters.

RADIO NEWS CLIP: The Solar Impulse 2 plane is currently tackling the most ambitious leg of its round the world journey.

RADIO NEWS CLIP: Once midway across the Pacific, there's no turning back, with no airports to land at and no boat capable of trailing the plane fast enough.

RADIO NEWS CLIP: Even to get one man across an ocean will push him and his machine to the limits.

BERTRAND PICCARD: We have now entered the first really critical part of the flight. He is now starting to reduce the power of the engines, that he starts to glide down. And he needs to save his energy as much as he can until the next sunrise.

NARRATOR: During the night, André will slowly descend, relying on the potential energy he gained from altitude and the plane's highly efficient glide. But at dawn, they'll be down to their last energy reserves. Just a thin layer of clouds could throw a wrench into all their energy calculations.

And if André comes up short, his only option is the inflatable raft under his seat and the hope that his G.P.S. beacon will guide a passing ship to his rescue.

WIM DE TROYER: Wednesday, there is bad weather coming in, thunderstorms. And afterwards it's turning northwest.

BERTRAND PICCARD: It's a, it's a wall in front of us?

ANDREAS FÜRLINGER: And we have one or two layers where we have stratocumulus. We will reach the point of no return in approximately 10 hours, so we have to have a decision by that point.

NARRATOR: They are fast approaching the point at which they can no longer turn back because of the prevailing winds.

BERTRAND PICCARD: The good side is that the plane flies well, André is in a good shape, and probably we can make it through the first night with enough energy. On the other hand, we're in deep (bleep), because we don't know how to cross the bad weather front in five days.

WIM DE TROYER: It's a big deception, actually. The problem is that cold front over the ocean. And at takeoff, we were confident we had solutions to, to cross it, and then we didn't have a solution anymore.

NARRATOR: André has now made it through his first night, but the cold front predicted for day five appears to be intensifying and becoming more hazardous.

ANDRÉ BORSCHBERG: (Translated from French) The second day begins after a very interesting night. From time to time, the auto-pilot alarm goes off and I must react immediately, so I am learning, little by little, to detach. And when I feel like I'm falling asleep, and it makes me a little afraid, it's then that I hope for confidence.

I hope they figure out the weather. It would be really hard to stop at this stage.

ANDREAS FÜRLINGER: So, you can confirm that it's blocked now?

CREW MEMBER: At that position?

ANDRÉ BORSCHBERG: At that position, yeah.

NARRATOR: The updated weather models now show that there is no clear passage through the cold front. André would have to descend through multiple layers of cumulus clouds, which likely contain moisture and will produce turbulence, a dangerous one-two punch.

LUC TRULLEMANS: The aircraft is going through all those clouds, not close, you know, but layers.

NARRATOR: But turning back to land also carries its own risks. Japan is their best option to divert, but they have no logistics in place for an unplanned landing.

André is in a holding pattern over the Sea of Japan, as they negotiate with several potential airports.

MICHAEL ANGER: Well, for me, it's clearly red to continue. It's no way. The earlier we announce this diversion, the higher is the rate of success, I would say, to save the airplane and the pilot and the mission.

BERTRAND PICCARD: My personal opinion is that we have more risk of losing the airplane in Japan than if we try to reach Hawaii. I don't see how we can get permission to inflate a mobile hanger in Japan.

MARKUS SCHERDEL (Safety Review Board): The airplane is not made to cross a front and fly in cumulus clouds.

BERTRAND PICCARD: Until when can we still say we try to cross?


Either we divert, or we take a big risk.

BERTRAND PICCARD: Nobody is confident to continue, so our position would be to make a diversion on Nagoya.

ANDRÉ BORSCHBERG: If there's no window, no go.

RADIO NEWS CLIP: The green energy plane, Solar Impulse 2, stopped moving towards its make-or-break next destination, Hawaii.

RADIO NEWS CLIP: There's no telling how long they're going to spend in Japan waiting on the weather conditions.

NARRATOR: It is an unwelcome diversion.

A small emergency crew is now in Nagoya with the mobile hangar, but they don't have enough people to set it up. And the forecast calls for rain and heavy winds.

ANDRÉ BORSCHBERG: (Translated from French) If the plane isn't protected tonight, it's going to rain tomorrow. Part of the plane is already broken.

We need to be able to get the mobile hangar assembly tonight. If we do not succeed, the risk is that we lose the airplane completely, and the risk is extremely high. It's not 10 percent chance, it's 90.

DYLAN GORTON (Electrical Engineer): What we need now is our hangar, you know, to prevent it from sun, wind and rain. We're pretty much struggling to keep it on the ground.

ANDRÉ BORSCHBERG: We need to put full speed on it; maximum speed, maximum efforts.

NARRATOR: Just ahead of the rain, the rest of the ground crew finally arrives and jumps into action.

NILS RYSER: The aircraft was not just a little bit wet. It was completely wet, with water dripping from every single part of this aircraft.

THOMAS SEILER: Well, we want to avoid a short circuit, because that would blow, very probably, the main fuse inside the battery.

Oh, (bleep). I didn't see that.

BERTRAND PICCARD: I hope it will be okay, but I don't know at this stage. Maybe in 3 months we're still in Japan. And then it would be a disaster for our flight around the world.

ANDRÉ BORSCHBERG: (Translated from French) It's your job to do this. I hired you for that. I understand you're very stressed out, but you have to understand we are obligated to rise above it.

NARRATOR: The team is grounded in Nagoya, for over a week, to fix the wing spar that broke in the heavy wind and ensure the airplane is completely dry.

ROBBI FRAEFEL: Checking if there is a little bit of water left in the structure. Parts which have water inside explode if the water gets frozen when we climb very high.

André would, would take all the risks. We, from the engineering, we want to reduce as much as we can to make his life safe, but he is a risky guy.

NARRATOR: Meanwhile, at mission control, the diversion to Japan poses a problem for the air traffic control specialists on the team: a crowded airspace with many restrictions, which they have to negotiate.

NIK GERBER (Air Traffic Controller): Flying at 35 knots in midst of traffic which flies at 500 knots, so, it's a little bit an obstacle, eh?

NARRATOR: The Japanese insist that Solar Impulse avoid red zones of peak air traffic and militarized areas, limiting their exit strategy.

BERTRAND PICCARD: We always want to wait for better windows, but now we have passed the 21st of June, and it's going to be worse and worse in term of energy. We are not on the safe side, if we wait.

NARRATOR: In preparation for takeoff, the ground crew begins taking apart the mobile hangar, as the press stands by.

YASEMIN BORSCHBERG: (Translated from French) It's going to be great, André. The flight is going to be magnificent.

NARRATOR: But the forecast takes an unexpected turn for the worse.

BERTRAND PICCARD: There is no high pressure there. It's a complete (bleep) weather. There is absolutely no way to go through it. To follow something for three days, and, and 10 minutes before the takeoff…crazy. There's really a problem somewhere in our way of working.

(Translated from French) Our latest weather report shows our way is blocked. We are waiting to see if Luc can find us a way out.


We're checking if we should proceed or not.

CREW MEMBER: How are you feeling?

ANDRÉ BORSCHBERG: Detached. That's the best way.

TAMARA TURSIJAN (Engineer): I think we really need it now, because the spirits are, sort of, not very well. And if we now take the plane back, assemble the mobile hangar again and stay here for longer, it's going to be quite bad for the general mood of the team, I think. So, that's why I believe we're going to take off. It's going to happen.

MICHAEL ANGER: This afternoon I was confident. Now, I feel more like gambling. If he has to bail out here, okay. Water's maybe already warmer, but I don't want to gamble with a pilot in the ocean.

RAYMOND CLERC: I'm not confident to letting, taking the risk of your life. It's very difficult to go against the inner, inner feeling.

BERTRAND PICCARD: There are two terrible situations. The worst is to be in the middle of the Pacific and see that it closes, and to lose the plane and you jump. The other one is to be on the runway and to see that it closes. And this is exactly what we have, but it's not as bad as if you are in the middle of the Pacific.

ANDRÉ BORSCHBERG: I feel that you went over the tipping point in terms of feeling, and so it must be right.

BERTRAND PICCARD: But it's a terrible situation, and I imagine, for you…I'm so sorry for you, André. You cannot imagine…

ANDRÉ BORSCHBERG: Don't be sorry.

BERTRAND PICCARD: You cannot imagine how sorry I am for you. You are in that cockpit, you are ready to go. When I said we have to stop, Michael told me, “Thank you.”

ANDRÉ BORSCHBERG: So confirm, flight is canceled. We go back to the tents unfortunately, but that's, that's life, eh? Lot of hurdles. Big hurdles.

BERTRAND PICCARD: We tried everything we could. We just failed the last centimeter, the last centimeter.

WIM DE TROYER: Always trying to make it, to make it work, and then you see that all that work is kind of for nothing. I have to admit that the last weeks I was, was losing, losing faith.

NARRATOR: With the summer solstice now behind them, the daylight hours and available energy to cross the Pacific are steadily decreasing.

ANDRÉ BORSCHBERG: The monsoon is really picking up here in Japan, which means rain. It's also the risk of a typhoon. So, what we are facing, if we cannot leave over the next few days to Hawaii, is being hit by a typhoon, lose the mobile hangar and, of course, lose the airplane.

MARKUS SCHERDEL: We will always have an unknown thing. I think this is the nature of a forecast. It's a forecast, it's not the truth.

RAYMOND CLERC: Either we try to cross an ocean or not.

NARRATOR: At last, it looks as though they can. A promising five-day window of clear weather opens up from Nagoya to Hawaii.

BERTRAND PICCARD: You know, it was so embarrassing to have André ready to take off, all the press watching, and we had to cancel at the last minute. And this time we want to avoid this, so we're not telling anybody. And once we're in the air, if it works, then we say, “Hey-o, cuckoo, here we are. This time it's going well.”

ANDRÉ BORSCHBERG: Okay. Third attempt, ladies and gentlemen, third time that we try to move.

(Translated from French) More discussions about whether to go or not, like the last time, on the tarmac are unacceptable. We're going.

Whatever happens, we go.

I am committed, completely committed to this flight. Point of no return is already past, long time ago.

GREGORY BLATT (Managing Director): Friday, we were both super, super depressed in Tokyo. This might be the end. And it's not sure we're going to still make it, but if we make it to Hawaii, at least we've done the hard thing.

NILS RYSER: We are just getting ready, and we try to take off at 3:00 a.m. sharp.

SÉBASTIEN DEMONT: This time it seems better, so we try again.

RAYMOND CLERC: Looking fine from here.

NARRATOR: Then, just minutes after takeoff, they hit a snag, this time with the plane's autopilot surveillance system, known as the M.A.S.

ANDRÉ BORSCHBERG: There was a short M.A.S. failure.

MICHAEL ANGER: Okay, copy. There was a short M.A.S. fail.

If we do not find out why it happened or what, what triggered it, we should not continue for the Pacific.

THOMAS SEILER: The biggest concern is, the problem is the M.A.S. That's the, that's the killer one.

BERTRAND PICCARD: The M.A.S. is the system controlling the autopilot, which is giving false alarms and waking up André each time he wants to sleep.

NARRATOR: The M.A.S. wakes up André if there is a significant change in the airplane's heading or bank angle. The false alarms are not just annoying, they keep André from getting the rest he needs.

If the system fails completely, he will have to rely on mission control to wake him up. But there's a chance he could lose satellite communication out in the middle of the Pacific.

THOMAS SEILER: So, you want to continue to Hawaii?


THOMAS SEILER: Knowing that the monitoring is not working?


THOMAS SEILER: And you still…you…

BERTRAND PICCARD: It makes life a little bit more complicated. We'll need the monitoring from the ground.

THOMAS SEILER: The risk is really high. The risk is really, really high. We have 55 minutes before the point of no return, and we don't know what is causing this. And we have no idea. I mean, it could degrade.

ANDREAS FÜRLINGER: We still don't know the cause of the problem.


MICHAEL ANGER: If we go back to Nagoya, I'm sure we would find another window, but the season is not over.

BERTRAND PICCARD: A bloody, (bleep) situation. If we go back to Japan, I think it's the end of the project.

NARRATOR: With the electronics malfunctioning, the engineers have serious concerns about continuing, but the pilots are concerned about what another aborted flight could mean to the future of the project.

BERTRAND PICCARD: (Translated from French) I think this is the end of the project if we go back to Nagoya.

ANDRÉ BORSCHBERG: (Translated from French) It's really complicated to continue. I think people will resign, so that will create a pretty big crisis.

BERTRAND PICCARD: (Translated from French) This is the most critical part of the project so far.

ANDRÉ BORSCHBERG: (Translated from French) We really need the whole team behind us if we are going to continue. How much time do we have?

BERTRAND PICCARD: (Translated from French) Twenty-six minutes. Raymond is organizing a meeting with the engineers, and we'll call you back.

Now, we just need to know if André wants to continue or not.

INTERVIEWER: And what do you think it will take for him to decide?

BERTRAND PICCARD: Guts. Not only as a pilot, but for, for the project.

NARRATOR: It's the most serious crisis they have faced, leading to a sharp division within the team.

THOMAS SEILER: We have an aircraft, which is not nominal. Things will break during this journey, and if we start the journey already with one redundancy down, that's not a good starting basis. I would recommend to go back.

BERTRAND PICCARD: Going back to Nagoya in the season of typhoons with the possibility of destroying the airplane on the ground, in term of overall project, it's more risky to come back than to continue.

ANDRÉ BORSCHBERG: Personally, I have a very good feeling I can do it. We have an airplane which has a very good source of energy. Very good storage.

MICHAEL ANGER: If you decide to continue, as a friend, you have all, all of my support, but as an engineer, I would say we have to go back as we have the choice.

BERTRAND PICCARD: A lot of people can be a little bit afraid, scared, by the unknown in which we're jumping. I was very often in my life in these type of situations, and I tell you it's worth it.

But the decision we take goes far beyond the flight itself. We have now the possibility to do what nobody has done. When Chuck Yeager broke the speed of sound, he had the broken rib. All these things were absolutely incredible feats.

PETER FREI: I think it's very dangerous, too, with this heroic speech, to encourage people to take a wrong decision, because we never have the story of those who got killed.

ANDRÉ BORSCHBERG: This is a hard project. These are difficult situations. I guess I do it because I know this airplane quite well, and what can be done and what cannot be done.

PETER FREI: Nobody, in the future, will understand that two managers can go against a whole team, and you really force us to support something that nobody wants to do.

THOMAS SEILER: I just want to make one point very clear. There's only so much we can do to support you from here, from the ground. So, when you decide to go on, you will be on your own up there.

CAPCOM: This is CAPCOM speaking. We have to start the climb now if we want to have a chance to respect the profile.



ANDRÉ BORSCHBERG: (Translated from French) It was pretty hard to decide. It really hit me in the bottom of my stomach, not really knowing if it was the right decision. Technically I think it was, but in relation to my family, to Yasemin, it's true, it's like, “Wow, this is not easy.”

MARCUS BASIEN: From an engineering point of view, it was the wrong decision, that you still can make. It is like, I don't know, driving with a flat tire.

ELEONORA GRAVA (Mission Engineer): We have to be lucky, from a certain point of view, but it's, it's their decision.

BERTRAND PICCARD: We saved the project by deciding not to return to Japan. On the other hand, we have some of the engineers who are so pissed off because we did not follow their recommendation, they want to leave the project. And I don't know what will happen after Hawaii.

NARRATOR: As morning comes, André continues to be awakened by false alarms.

ANDRÉ BORSCHBERG: So, I lost one source of information.

Well, let's see, we are currently rebooting.

ANDRÉ BORSCHBERG: A lot of wake up calls in this, in this airplane.

CHRISTOPH SCHLETTIG (Flight Director): This M.A.S. system, which monitors the aircraft while the pilot is resting, is behaving erratic. We had it working in the beginning, then it produced a failure, so we shut it down. We tried again. We don't really know what the status of the system is.

ANDRÉ BORSCHBERG: The first night was about digesting, I mean, the emotion of the first day. It was really intense. When I look out, you know, I see the moon, I see the clouds, and here I am over the Pacific. I think I feel a bit higher.

NARRATOR: On day two, there's a worrying new development: the plane's batteries are overheating.

CHRISTOPH SCHLETTIG: We need to burn more energy.

CHRISTOPHE BÉESAU: It is a risky game to…


MICHAEL ANGER: Due to the flight profile we did on the first day, the batteries got too warm. If it sums up over the days, it can become really too hot. They can start to burn.

NARRATOR: Climbing too quickly on the first day increased the demand on the batteries, and they began to overheat. The risk is that this could degrade their performance.

MICHAEL ANGER: Today, the challenge is to keep the battery temperatures low, as low as possible. So, we will adjust the climb profile to not have too much current going into the batteries.

RAYMOND CLERC: It's turbulent since, I think, about one hour. We are climbing again at 9-0, and we'll see if it's better, but it costs energy.

ANDRÉ BORSCHBERG: That's exactly what I was afraid of.

RAYMOND CLERC: Still some time until the next sunrise.

ANDRÉ BORSCHBERG: Turbulences during the night, which means a lot of work, of course with no auto-pilot, of course no sleep. I really started to work hard to see how we could get out. So we climbed again, and when you climb you use the energy that you need for the night, so it's a little bit stressful.

MICHAEL MCGRATH (Cockpit Systems Engineer): We're monitoring every day how many resting periods is he getting. For the first two nights, he had three hours of sleep. That's okay, but we don't know what's going to happen on day four, if you keep that rhythm, and day five.

So, we climb every day the equivalent of sea level straight up to Mt. Everest. No acclimatization. If you don't have enough oxygen, there's the risk of hypoxia. Within 60 seconds, will lead to a severe degradation in your ability to understand what's going on around you. You become euphoric. So, not only are you in a dangerous situation, you're not able to recognize the situation and you feel good about not recognizing the situation. Then, very quickly, you, you will pass out.

We're watching to see how his body is absorbing the oxygen. Is it actually getting enough? And you're constantly listening to this “shoosh, shoosh.” You hold your breath and hope he breathes, and then you keep going.

LAILA FATHI: Pilot status: mood, he is exhausted; not as good as it was.

MARCUS BASIEN: We have a pilot that is starting to show signs of fatigue. We have batteries that will not take a lot more abuse. We see that all the systems are stressed, yeah? The flight is not over.

THOMAS SEILER: Quite intense. You have to perform, because it's real-time, you know. As an engineer, you are used to, “Okay, I solve the equation today, and if I don't solve it today, then I'm going to solve it tomorrow.” And this is totally different. I'm kind of happy that it's soon over.

ANDRÉ BORSCHBERG: So now, a preparation for landing. I was thinking about all this, and I cried. Cried loud. It was a little bit ridiculous, you know, alone in the cockpit crying, everything was going well, but it was so, so intense.

CHRISTOPHE ETTER: (CAPCOM): And André, you have some kind of headache?

ANDRÉ BORSCHBERG: No, no headache, but something's been growing on my head. Really strange.

CHRISTOPHE E: Okay, but I cannot see. Do you have the face view? Now? Oh, okay. He looks terrific, yeah.

ANDRÉ BORSCHBERG: I don't know what happened. I spent too much time in this damned plane.

YASEMIN BORSCHBERG: (Translated from French) André, how is it going?

ANDRÉ BORSCHBERG: (Translated from French) Very good, very good.

ELÂ BORSCHBERG (André Borschberg's Daughter): He can feel every, I think, element in the plane. He knows which wings is vibrating. I think he was a bird in another life.

RADIO NEWS CLIP: A plane, powered only by sunlight, makes history today in a five-day journey across the Pacific.

RADIO NEWS CLIP: This will be the furthest a solar plane has ever flown, as well as the longest lasting solo flight in aviation history.

GIRL WAITING FOR SOLAR IMPULSE: I've never been to something this historical before. I'm too young to see other things, just the right age to see this.

CAPCOM: It's absolutely beautiful, and the latest wind from the ground crew is 0-4-0-3 knots, in the axis.


GREG BLATT: (Translated from French) Sixteen years, Bertrand.

BERTRAND PICCARD: (Translated from French) I think in the 16 years, the last two months have been the hardest.

CAP COM: To confirm, you have the landing and promotion lights on.

ANDRÉ BORSCHBERG: (Translated from French) It's nice to put them on.


ANDRÉ BORSCHBERG: I feel secure.

(Translated from French) It's fabulous.

BERTRAND PICCARD: (Translated from French) You've really built a wonder.


YASEMIN BORSCHBERG: Do you feel okay?

ANDRÉ BORSCHBERG: To fly with the sun, you need to be extremely energy-efficient and this efficiency can be used everywhere.

BERTRAND PICCARD: This is why it's a historic first for aviation and a historic first for renewable energies.

MEMBER OF THE PRESS: Will you make it around the world? Are you confident of that?

BERTRAND PICCARD: It's an attempt. We cannot be overconfident.

ANDRÉ BORSCHBERG: I received so much support from people I didn't know, and the beautiful message. So, when you read this, you know, you know that people are supporting you. And I was carried by all this, I'm sure.

ROBBI FRAEFEL: All of us were very lucky to have the pilot back, but when this decision came up that André and Bertrand want to continue, it hurt us in the soul that somebody decided against us.

PETER FREI: I was fully in opposition to André and Bertrand. André is pushing. We always had these discussions and fights, “Why do you tend to go beyond limits all the time?” We engineers tried to set reasonable limits that you survive, and you, your target is always to sort of prove us that we set the limits too narrow.

ROBBI FRAEFEL: If everybody is telling you that you are a hero, I think it's good also, for them, that there are people who try to pull them back and on the ground from time to time.

NARRATOR: Despite the divisions and problems with the plane, they are still hoping to get around the world this year.

Their immediate worry is the health of the batteries.

ROBBI FRAEFEL: The concern about the batteries is that they are damaged. We heated up the battery in only one hour by about 20 degrees. At the moment, we are on the worst-case scenario, where we have to exchange some cells in the batteries, which is, this is a nightmare.

BERTRAND PICCARD: We have overheated the batteries. More cells are damaged than the spare parts we have, so the logical consequence is that we will stay here until next April, where we can continue.

ANDRÉ BORSCHBERG: The flight from Japan to Hawaii left scars on many of the engineers. I think for everybody to complete this flight around the world is extremely important. It's part of their part of their life. I mean, they all stayed.

NARRATOR: During the break, new batteries had to be manufactured in Korea.

The engineers realized that the batteries were over-insulated against the cold and heating up too much in warm conditions, so they engineered a two-way valve system that allows the pilot to let the heat out.

BERTRAND PICCARD: Last year, I was too much emotionally involved. I was thinking, “It's now or never,” and I was completely the head under the water, which is really not good for flying an airplane over oceans, you know?

I lost the mask, one, sat up.

I've flown 20 days in a balloon, but we were two. Flying alone, it's something different.

NARRATOR: To prove he could fly safely over several nights, Bertrand trained to rely more on instruments than on the horizon.

BERTRAND PICCARD: One, two, three, the fourth one.

I will never be as precise as a jet fighter pilot. This you cannot get at my age, but at least to do it correctly.

Climb, 174.

NARRATOR: After studying potential routes from Vancouver to Mexico, the team locks in on a three-day flight path to Moffett Field, home of NASA, just south of San Francisco.

GREG BLATT: We see a weather window for Moffett, right now. It looks good. It's a short flight. Okay? We'll only confirm, really, tomorrow, even on the day of takeoff.

BERTRAND PICCARD: It comes from the house of Charles Lindbergh in Maui; a beautiful gift. This is more for the Americans than for the Europeans: and it's Star Trek, Captain Picard, who is inspired from the twin brother of my grandfather.

It was a challenge to be an explorer that would be different than my father and my grandfather, not to just redo the same.

CHRISTOPHE ETTER: The wind is at the limit, so, for the time being, we don't go out.

BERTRAND PICCARD: I was doubting sometime, is it my way? Because I'm also interested by psychology, spirituality.

CHRISTOPHE ETTER: Good Morning, Bertrand. This is Christophe. How are you?

BERTRAND PICCARD: I'm fine. I had four hours of good sleep. I woke up before the alarm clock. I'm in perfect shape.


BERTRAND PICCARD: My father and my grandfather gave me the drive to be an explorer, but my mother showed me the need to give it meaning. We were extremely close, like two human beings in quest of understanding why we were on this earth.


Have a great flight, Bertrand, and enjoy it. And don't forget to come down.

MICHÉLE PICCARD (Bertrand Piccard's Wife, Director of Communications): People are always thinking I am the wife, I should have this fear. When Bertrand did his round the world balloon flight, our children were very small. At this age, children, they don't have any fear. They are just living the present moment, and I just realized I should not give them this fear.

RAYMOND CLERC: The flight is long for him. This was one of his main question: if I don't sleep, how can I survive?

BERTRAND PICCARD: First sunrise over a sea of clouds. That's the sunrise I will remember all my life.

Switching on the solar generators. I can show you my little house. That's the kitchen, where I prepare my food. The toilet inside the seat. That's the cellar. Breakfast. The family, Estelle, Oriane, and Solange, Michelle.

ESTELLE PICCARD (Bertrand Piccard's Daughter): (Translated from French) Hello, Papa?

BERTRAND PICCARD: (Translated from French) Hello, is this Oriane?

ESTELLE PICCARD: (Translated from French) There's Oriane, Solange and me at Mission Control, Monaco, to say hello.

BERTRAND PICCARD: That's fabulous. We've been waiting so long for this flight.

BAN KI-MOON (Secretary General of the United Nations): Hello. Hello Solar Impulse, hello Captain Piccard.

BERTRAND PICCARD: Good afternoon, Mr. Secretary General. I speak to you from the cockpit of Solar Impulse in the middle of the Pacific, flying on solar power. All this airplane is like a smart grid, collecting energy, distributing energy, with very, very high efficiency. And this is exactly what the world needs.

BAN KI-MOON: Wonderful. You look like an astronaut in the moon.

BERTRAND PICCARD: Thank you, Mr. Secretary General, and congratulations for what you are doing. The world will remember it.

BAN KI-MOON: While you are making history, we have also made history today. More than 175 countries signed the climate change agreement. Thank you for your leadership and inspiration. All the best to you. Bon voyage.

BERTRAND PICCARD: I think I had more butterflies in the stomach before that live transmission than when I took off with Solar Impulse three days ago.

The sun's going to arrive in a few minutes to carry me to San Francisco. It's beautiful. Moment extraordinaire.

Fourteen last years of attempts, of setbacks, of problems, it was worth going through all these moments just to be here, now.

ALAN EUSTACE (Former Senior Vice President of Knowledge, Google): The thing that amazes me is the size, and especially given the low weight. This is the moment where you start to see electric power taking off.

BERTRAND PICCARD: Sometimes, you know, there are people who will say, “Why do you fly with a solar airplane like Solar Impulse? It's expensive, it's big, it's slow, only good weather and only one person in it.” Silicon Valley, nobody asks; everybody knows, understands.

When Solar Impulse landed yesterday in Phoenix. It was just in front of a cemetery of old airliners.

ANDRÉ BORSCHBERG: It's very sad. A lot of these airplanes will never fly again, you know, they get dismantled. This one lost, you know, the left eye. Crazy. Of course, it's normal. All this will be replaced by better technologies. But still, in fact, I feel emotions when I'm here. An airplane is not just a piece of metal. It represents much more.

BERTRAND PICCARD: When people think fuel is forever, they forget the Gold Rush, 100 years ago, and the ghost towns. I'm not saying Solar Impulse will replace an airplane like that very soon. In 10 years' time, we have airplanes flying electric with batteries, plugged in the grid before takeoff, and they will transport 50 people.

Today, you make electricity with solar panels in Dubai cheaper than with gas.

Ladies and gentlemen, you are now doing your last flight on the combustion engine airplane. In the future, you will be flying electric.

NARRATOR: At mission control there is no time off. The team has one focus: getting across the U.S. as fast as possible so they can cross the Atlantic during the peak energy days of summer.

They will have to navigate around the turbulent air over the Rocky Mountains, the unstable thermals of the Southwest and the Midwest's infamous “Tornado Alley.”

WIM DE TROYER: Well, we are right in the tornado season. Every, every two or three days there are thunderstorms, and those thunderstorms, they can lead to tornadoes.

VISITOR #1 TO SOLAR IMPULSE: The local news came on and said this was landing, so I went outside and watched the skies to try to see something weird.

VISITOR #2 TO SOLAR IMPULSE: All night long.

VISITOR #3 TO SOLAR IMPULSE: I don't buy into the global warming deal, just to be honest. We've had oil and gas for all these years, but if they can make stuff battery-powered, then I'm all for that. They can obviously make it go faster, because I think you can drive faster from Phoenix to Tulsa than he flew, but it's a start.

RADIO NEWS CLIP: Just as the Wright brothers did before them, this team hoping to show anything is possible with the right resolve.

NARRATOR: But in Dayton, Ohio, a problem with the mobile hangar reminds them just how fragile their plane is.

ANDRÉ BORSCHBERG: Well, we had a failure in the electric system of the mobile hangar. It deflated, touched the airplane. It can destroy the airplane, eh?

NILS RYSER: The mobile hangar was laying on the tail of the aircraft, slowly going down onto, onto the wing.

BERTRAND PICCARD: I just would like to hear if there is a visual defect.

CREW MEMBER: We have no idea what, especially, here I'm not so afraid, but from the wing.

BERTRAND PICCARD: Until we see there is a problem, it's stupid to cancel the flight of tomorrow.

ANDRÉ BORSCHBERG: Don't even think about it. I hope we can fly again. I think that's where we are.

NARRATOR: Even though there may be no signs of external damage, the weight of the collapsed hangar may have cracked the plane's internal structure.

ANDRÉ BORSCHBERG: What we try to avoid is that we get into a panic stage. Bertrand is pushing of course.

Don't push this. Don't push. It's not the moment. We try, we go step by step.

BERTRAND PICCARD: So, for me, for me, it's a non-event.

ANDRÉ BORSCHBERG: It's not a non-event. Be careful what you say.

We are in deep (bleep). In really deep (bleep). Maybe there is nothing on the airplane, but we don't know. This is an airplane that's certified to fly over the major cities, and you don't play with safety. That's the responsibility of the engineers. And I don't think we will come with an answer which is black and white.

NARRATOR: To be sure the plane has no structural damage, they must calculate the suspected load on the tail and wing.

BERTRAND PICCARD: This project is too big to be run just by personal wishes, but this is very new for me.

NARRATOR: After crunching the numbers through the night, the engineers finally decide that the plane is safe to fly.

ANDRÉ BORSCHBERG: We had a couple of explosions, very often because of our character. Maybe because of our egos, and it was a hard process. I think we understand that we bring to each other much more than the difficulty that the relationship creates.

BERTRAND PICCARD: I don't think we're ever going to laugh at the difficult moments we went through. With André, we are together since 13 years on this project. We're very proud that we didn't split apart, that we didn't have any divorce, that we could learn so much from each other.

NARRATOR: As they arrive in New York, Bertrand is reminded of the triumphs and struggles of his father, Jacques Piccard.

BERTRAND PICCARD: In 1969, my father arrived with his submarine. After the drift mission of one month in the Gulf Stream, he arrived in front of the Statue of Liberty. I was 11 years old, so happy and proud.

You know, altogether he had 50 projects of submarines and only five got some fundings. I saw my father worn out by all this disappointment. He told me, “Don't feel obliged to continue my work.”

NARRATOR: Now, the Atlantic Ocean looms large. Bertrand faces perhaps the biggest challenge of his career. It's smaller than the Pacific, but with notoriously harsher weather. There's a cold front in their way, a wall of clouds and unstable air that's risky for the airplane.

After days searching, mission control in Monaco notices a narrow corridor of clear skies starting to form, leading to Seville, Spain.

WIM DE TROYER: The corridor that we've been following, and that's, it's really small, between all the bad weather to the north to the south.

NARRATOR: But they only have so much time before it closes.

BERTRAND PICCARD: Let's go for the Atlantic, my friends.

The Atlantic is going to be probably the greatest flight of my life. I don't want to put the pressure and say, “Oh, I met Charles Lindberg when I was a child, and imagine how important it is and how symbolic it is.” I want it to be natural. I want it to happen in a peaceful way.

When you are in the middle of the unknown, you have these moments of grace. You are at that moment like you would like to be forever.

RAYMOND CLERC: So, now you are challenging your fighter pilots.

BERTRAND PICCARD: I love my fighter pilots.

Did I show you my map already? Maybe André will not like this map as much as me because the Pacific is very small on this map but the Atlantic is very big.

WIM DE TROYER: In front of you, the window is still open, behind you, the window has closed.

NARRATOR: Bertrand makes it through the corridor just in time.

Next, he must harness the powerful winds of the jet stream to propel him towards the coast of Spain.

LUC TRULLEMANS: Jet stream is the conflict between cold air in the upper levels and warm air, and they are pushing against each other. At 20,000 feet we may have 50 to 60 knots pushing the aircraft to the east, to Europe. And now we will fly very fast, eh?

RADIO NEWS CLIP: An airplane powered solely by the sun has made aviation history after an almost three-day flight across the Atlantic from New York.

RADIO NEWS CLIP: From Seville, the aircraft will continue its journey back to Abu Dhabi, where it all began for this extraordinary project.

ANDRÉ BORSCHBERG: When I flew, yesterday, over the pyramids, they were just emerging out of the haze. I guess it was exactly the same as they were 4,500 years ago. They believed in eternal life, and for me it's a symbol of eternity. Solar Impulse is also intended to be a symbol, a symbol about sustainability, a symbol about the potential of renewable energy.

If you build something like this, which is done to be forever, it's not necessarily the solution which we would go for. Sustainability means that you stay in line with nature, and I'm not sure, in fact, the way we build takes this into account.

If you don't change the situation, the world will dictate you the future, and not the other way around.

BERTRAND PICCARD: There are so many mixed thoughts and feelings right now that it's difficult. After this flight, it's over, so it's like a family that's going to split.

But there is the message. And what we have to do out of this flight, and I'm working since years for that, and for that moment, and I want to be sure not to waste it.

NARRATOR: After 16 months, and nearly 25,000 miles, the last leg to Abu Dhabi presents an unexpected, final challenge. They knew it would be hot in this desert region, but now an extreme heatwave is posing a dangerous threat.

LUC TRULLEMANS: We never flew such a light aircraft also in such conditions, extreme conditions.

NARRATOR: Above the Saudi Arabian peninsula, night temperatures at 3,000 feet hover around 90 degrees. Mission engineers worry that critical systems on board, which are not certified for such heat, could completely shut down. But their bigger concern is energy.

As the hot air cools during the night, it creates strong downdrafts of wind that push the plane to lower altitudes.

LUC TRULLEMANS: I didn't expect such an issue at the end, with the last leg. The downdrafts are so strong that he cannot fly through the night. He will use so much energy to stay at this level that he cannot survive during the night.

CAP COM: Takeoff conditions on Sunday are not good, and we will have extreme thermals overhead.

BERTRAND PICCARD: I believe that each of the problems can be solved.

PETER FREI: There is a danger that you overheat equipment, and, at the end, you have a failed aircraft.

NARRATOR: After several days waiting, the severe downdrafts appear to be subsiding. It looks like the flight is back on.

MICHAEL ANGER: As we are quite tight on energy, timing is critical.

WIM DE TROYER: Every day there are cumulus clouds that are really, really high.

MICHAEL ANGER: Is the pilot healthy?

BERTRAND PICCARD: This time the pilot is a little bit green, I have to say.

MICHAEL ANGER: You mean it's stomach problems or…?

BERTRAND PICCARD: Yeah, yes. I'm a little bit weak, but the general, general situation is good.

MICHAEL ANGER: Okay, then drink a lot of water, but you're the doctor, not me.

Keep in mind that the flight is not easy, yeah.

BERTRAND PICCARD: No, it's a difficult flight. I know. Absolutely.

Everything is different from what we have planned. It's adventure. It's not a business plan.

CREW MEMBER: Bertrand, are you okay?

BERTRAND PICCARD: It's not the moment I'm the healthiest in my life, but it's still under control. Still under control.

ANDRÉ BORSCHBERG: (Translated from French) Nobody. How do you feel?

BERTRAND PICCARD: (Translated from French) Listen, I just felt bad for a moment.

ANDRÉ BORSCHBERG: You have two big days ahead of you. I think it's a good idea not to continue.

BERTRAND PICCARD: I hope it's the last taxi, because if it is, then it's fantastic moment right now. I've never been in a project that gave as many moments of elation and moments of disappointment. It's really strange.

It's really difficult.

(Translated from French) Bloody hell.

CAP COM: As we told you, the night might be quite tough for you.

BERTRAND PICCARD: I would like to drink; I would like to pee; I would like to remove some clothing, because I'm too hot; but I just can't do anything else.

NARRATOR: During the night, Bertrand must try to ride the updrafts and avoid the downdrafts that will sap his energy reserves.

JULIAN KRÖNERT (CAPCOM): Once you have an updraft, just go with it, and don't fight the downdraft with power. Just let it go.

ANDRÉ BORSCHBERG: It was not such a bad idea that you had 17 years ago.

BERTRAND PICCARD: You know what, it became a good idea, thanks to all the people who supported it.

THOMAS SEILER: We can't save the planet with one plane flying around the world, but maybe it inspires many people to start solving problems instead. Then maybe it was worth all this stress.

ANDRÉ BORSCHBERG: We are late. We really have to move, gentlemen.

OFFICIAL ON GROUND: How you will enter? I don't have a …You don't have a permit to enter.

ANDRÉ BORSCHBERG: I will go, I'm the pilot. I tell you, I will go. You can shoot me. I will go and I will take my team.

BERTRAND PICCARD: When André took off the 9th of March last year, I was thinking, “We are completely crazy.” And a year and a half later, you see the result of what our team has achieved because they accepted to dream. And when you see the state of the world today, it is a crime not to try something. Not to try to increase quality of life on this planet. We love to fly. For others, it's in art, in science, in the community, but we have to try.

ANDRÉ BORSCHBERG: What I remember is to be on this runway 15 months ago exactly at this position, ready for the flight around the world, not knowing what would happen, not knowing how much time it would take, just go. Just go and start.

And seeing the airplane coming, it's like slowing down the time. It's really, really strong.

BERTRAND PICCARD: We did it! Wonderful! Wonderful!


ANDRÉ BORSCHBERG: (Translated from French) We are not going to open the door right away, eh?

We have the time, eh?

Pretty soon. We have the time.

Broadcast Credits

Quinn Kanaly & Noel Dockstader
Ian Reinhard
Angus Macqueen
Dana Nachman
Chris Schmidt
Noel Dockstader
Jean Kawahara
Christie E. Herring
Mathieu Czernichow
Yoann Le Gruiec
Daniel Meyers
Payam Azadi
Noel Dockstader
Jón Bjorgvinsson
Noemi Renevey
Antoine Bosson
A Productions UK
Dave Tweedie
Lane West
Michelle Sosa
Ashley Pagán
Leo Hallal
Ashley Pagán
Paul James Zahnley, CAS
Heart Punch Studio
Kim Aubry
Meghan Driscoll
Mary Gribben
Nicole Olivier
Adrianne Anderson
Joseph Dockstader
Leigh Anu
Gedeon Programmes
Borschberg Family
Piccard Family
Getty Images
The Garfield Kennedy Company
Musée Du Léman
Solar Impulse
ABC 15 Arizona
Al Jazeera
Arirang News
CBS / Local 12 Cincinnati
France 24
RTE News
Solar Impulse
WDTN Dayton, 2 News
Peter Frei
La Souris Verte
Solar Impulse Foundation 
The Swiss Embassy
Justine Jacob
yU + co.
Walter Werzowa
John Luker
Musikvergnuegen, Inc.
Ray Loring
Rob Morsberger
The Caption Center
David Bigelow
Kristine Allington
Tim De Chant
Cory Allen
Eileen Campion
Eddie Ward
Jennifer Welsh
Dante Graves
Lindsey Chou
Linda Callahan
Vanessa Ly
Ariam McCrary
Sarah Erlandson
Janice Flood
Susan Rosen
Lauren Miller
Brian Kantor
Michael H. Amundson
Kevin Young
Nathan Gunner
Caitlin Saks
David Condon
Pamela Rosenstein
Elizabeth Benjes
Evan Hadingham
Melanie Wallace
Laurie Cahalane
Julia Cort
Paula S. Apsell

A NOVA Production by Far West Film Co. for WGBH Boston

© 2018 Far West Film Co., Inc. and WGBH Educational Foundation

All rights reserved

This program was produced by WGBH, which is solely responsible for its content.

Original funding for this program was provided by Draper, the David H. Koch Fund for Science and the Corporation for Public Broadcasting.


Image credit: (Solar Impulse)
© Jean Revillard/Solar Impulse


Michael Anger
Lead Mission Engineer
Marcus Basien
Safety Review Board / Head of Flight Test
Christophe Béesau
Simulation Expert
Gregory Blatt
Managing Director
André Borschberg
Pilot, Co-founder Solar Impulse
Elâ Borschberg
André's Daughter
Yasemin Borschberg
André's Wife
Raymond Clerc
Mission Director
Wim De Troyer
Sébastien Demont
Lead Electrical Engineer
Alan Eustace
Former SVP of Knowledge, Google
Robert Fraefel
Head of Airplane Development
Peter Frei
Lead Designer
Dylan Gorton
Electrical Engineer
Eleonora Grava
Mission Engineer
Phillipe Manuel
Deputy Flight Director
Michael McGrath
Cockpit Systems Engineer
Ban-Ki Moon
Secretary General
Bertrand Piccard
Pilot, Initiator Solar Impulse
Michéle Piccard
Bertrand's Wife, Director of Communications
Nils Ryser
Head of Ground Operations
Christoph Schlettig
Flight Director
Thomas Seiler
Head of Energy & Propulsion
Luc Trullemans
Lead Meteorologist
Tamara Tursijan

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