The Deadliest Plane Crash

Making Air Travel Safer

Ironically, the very airplane crashes that give air travelers the most pause serve as the chief catalysts for increased safety, as most key improvements to flight protocols and equipment follow large-scale investigations into the most terrible disasters. The 1977 crash in Tenerife, the worst commercial aviation accident in history, was no exception. In this overview, learn about a handful of major crashes, beginning with Tenerife, that resulted in extensive inquiries and consequent changes. While safety experts caution that much still needs improvement—including reducing the more than 300 runway incursions that occur in the U.S. alone each year—these changes have made flying safer than ever.—Lexi Krock

KLM Flight 4805 and Pan Am Flight 1736, March 27, 1977

This crash remains the deadliest ever, claiming the lives of 583 people when two 747s collided on a foggy runway on the island of Tenerife in the Canary Islands. It occurred after a series of miscommunications between the two flight crews and Air Traffic Control (see The Final Eight Minutes). The KLM plane initiated takeoff while the Pan Am plane, unseen in the fog, was taxiing midway down the same runway. As the KLM plane began to lift off the tarmac, the lower part of its fuselage struck the upper fuselage of the Pan Am plane, which was in the process of turning off the runway. After Tenerife, officials made sweeping changes to international airline regulations, requiring that all control towers and flight crews worldwide use standardized English phrases. Also, cockpit procedures were modified so that the hierarchy among crew members was deemphasized and decision-making by mutual agreement was the rule. Known in the industry as "crew resource management," this modus operandi is now standard worldwide.

Avianca Flight 52 | January 25, 1990

This Boeing 707 on service from Bogota, Colombia, crashed while approaching its destination at New York's JFK International Airport. Seventy-three of the 158 people aboard were killed. The accident occurred after the plane flew in a holding pattern for 77 minutes while awaiting landing clearance at JFK and ran out of fuel. The NTSB attributed the crash to the failure of the flight crew to manage the aircraft's fuel load and to communicate to ground controllers what had become an urgent fuel situation. The board also criticized the airline for failing to provide the crew with the latest wind shear information in New York, which could have helped the pilot anticipate landing delays there and plan for an alternative destination. The FAA subsequently mandated stricter flight planning and communication requirements for all foreign carriers operating in the U.S.

USAir Flight 427 | September 8, 1994

It took one of the longest air crash investigations in U.S. history to determine what happened (if not why) to cause this accident near Pittsburgh, Pennsylvania, which killed all 132 people aboard. En route from Chicago, the Boeing 737 went down in a wooded area 10 miles north of its destination at Greater Pittsburgh International Airport just seconds after the captain declared an emergency. In its final report released five years after the crash, the NTSB concluded that the aircraft's rudder, a moveable control surface hinged to the tail fin, became jammed for still unknown reasons, forcing the plane into an almost vertical roll at about 3,600 feet. NTSB recommendations prompted Boeing to completely redesign the 737's rudder control system and revise the aircraft's flight manual to include a procedural checklist for pilots faced with rudder-control problems.

American Eagle Flight 4184 | October 31, 1994

Heavy air traffic and poor weather postponed the arrival of this flight at Chicago's O'Hare International Airport, where it was to have landed en route from Indianapolis, Indiana. The ATR-72, a twin-engine turboprop carrying 68 people, entered a holding pattern 65 miles southeast of O'Hare, which it maintained for over an hour in freezing rain. As the plane circled, a ridge of ice formed on the upper surface of its wings, eventually causing the aircraft's autopilot to suddenly disconnect and the pilots to lose control. The ATR disintegrated on impact with a field below, killing everyone aboard. Following an NTSB investigation, the FAA required that all ATR aircraft be fitted with expanded de-icing equipment. It also issued 18 "airworthiness directives" for all pilots operating small commuter aircraft, instructing them on how to recognize and respond to dangerous icing conditions.

American Airlines Flight 965 | December 20, 1995

Just 40 miles from its destination in Cali, Colombia, this nighttime flight from Miami, Florida, careened into the crest of an Andean mountain at about 8,900 feet, killing all but four of the 163 people aboard. Investigators identified a series of operational errors committed by the flight's two pilots. Their primary mistake was failure to correctly input heading instructions into an automated Flight Management System, which brought the airplane into an unfamiliar and dangerous landing approach. Furthermore, the inquiry found the 757's Ground Proximity Warning System to be inadequate. The investigation report introduced the issue of pilots' potential overreliance on automated flight systems and motivated the NTSB to make sweeping recommendations to address this problem. As a result, the FAA ordered most American-registered passenger aircraft to use an Early Ground Proximity Warning System to add redundancy in this area. It also ordered standardization of the input codes for electronic navigational systems worldwide.

ValuJet Airlines Flight 592 | May 11, 1996

This tragedy, which caused the deaths of all 110 people aboard, led to significant aviation policy changes, a 24-count criminal indictment against the airline's maintenance contractors, and, ultimately, the downfall of the carrier. The crash occurred in the swampy Florida Everglades shortly after the DC-9 took off from Miami International Airport en route to Atlanta. An uncontrolled fire broke out in the cargo hold and disabled the plane's electrical system. NTSB investigators determined that volatile oxygen-generating canisters incorrectly labeled as empty and illegally stowed by maintenance technicians in the jet's cargo hold exploded, unleashing an inferno. After ValuJet 592, all planes would be retrofitted with smoke detectors and fire-suppression equipment in cargo holds. Furthermore, the FAA enacted stricter rules regarding the transportation of hazardous materials by air and banned chemical oxygen canisters. Finally, it initiated a formal review of its own procedures for overseeing airlines' maintenance contractors.

TWA Flight 800 | July 17, 1996

Flight 800, a Boeing 747 flying to Paris from New York's JFK International Airport, plunged into the ocean off Long Island, New York, after a catastrophic break-up shortly after take-off. None of the 230 people aboard survived. With the Summer Olympics set to begin in Atlanta in two days, speculation of a terrorist bombing immediately arose. But after one of the most intricate inquiries in aviation history, which included the first full-scale re-creation of a downed aircraft from its debris, NTSB investigators ruled out terrorism. They focused instead on the aircraft's near-empty center fuel tank, where, they determined, an explosion of still unknown origin brought the plane down. The NTSB's recommendations focused on the flammability of the 747's fuel tank, including its potential ignition sources, design, and certification standards, and on the maintenance and aging of the aircraft's other systems, particularly wiring and fittings that could spark or overheat. Within two years of the crash, new fuel-management procedures were required for all 747s.

Swissair Flight 111 | September 2, 1998

This flight on an MD-11 plummeted into the sea off Nova Scotia, Canada, while traveling from New York to Geneva at night (see NOVA's Crash of Flight 111 Web site). All 229 people on board were killed. The crash occurred after the pilot radioed that there was smoke in the cockpit and requested an emergency landing. As he dumped the aircraft's fuel, vectored for a runway at Halifax's airport, and reported an escalation of the emergency, Flight 111 disappeared from radar. After a four-and-a-half-year investigation, which revealed evidence of an in-flight fire above the cockpit caused by faulty wiring and fueled by flammable airframe insulation, Canada's Transportation Safety Board published its final recommendations. These included toughening flammability standards for all materials used in airplanes and more stringent testing and certification of electrical wires. The FAA ultimately issued an order requiring the replacement of insulation in 700 commercial jetliners in the U.S., including every MD-11 in service. At least 500 other MD-11s worldwide were also modified. (For more on the investigation and its aftermath, see Dissection of a Disaster. See also Update on FAA Regulations.)

Alaska Airlines Flight 261 | January 31, 2000

All 88 people aboard perished when this MD-83 aircraft nose-dived with devastating force into the Pacific Ocean off southern California. Flight 261 had left Puerto Vallarta, Mexico, and was en route to San Francisco when it ran into trouble. At 28,000 feet, the crew reported problems with the plane's stabilizer trim (small flaps on the horizontal portion of its tail) and were unable to control the pitch of the aircraft. Moments later, they began an uncontrolled descent. In its investigation, the NTSB found that too little grease on the jet's jackscrew, a tail component that helps move the plane's stabilizer, had promoted excessive wear on its threads. Their report blamed Alaska Airlines for shoddy maintenance standards and the FAA for approval of these standards, which increased the likelihood of inadequate greasing. Changes have since been made to Alaska Airlines' maintenance procedures and the FAA's oversight apparatus, but federal prosecutors eventually opened a criminal probe into the crash.

American Airlines Flight 587 | November 12, 2001

Just two months after the four airplane disasters of September 11, 2001, an Airbus A-300 taking off from New York's JFK International Airport for Santo Domingo, Dominican Republic, crashed into a neighborhood in Belle Harbor, Queens, immediately raising fears of another terrorist attack. Five people on the ground and all 260 people aboard the plane were killed. The NTSB ruled out terrorism, focusing instead on the plane's vertical tail stabilizer and rudder, which snapped off as the plane fell from the sky. Several months after the accident, the NTSB issued two safety recommendations involving the A-300's vertical stabilizer and rudder, pointing out that some maneuvers can lead to structural failure. As a result of the warnings, Airbus is addressing these issues and American Airlines has implemented regular inspections of the tail sections on all its A-300s.

Enlarge this image
Flight 52

New regulations enacted after aviation disasters, such as this one involving a depleted fuel supply, help prevent future crashes.

Enlarge this image
Flight 4184

Following the investigation of American Eagle Flight 4184, all ATR-72s were retrofitted with additional de-icing equipment.

Enlarge this image
Flight 592

With small pieces of debris spread over a large swath of swampland, NTSB investigators said the recovery site of ValuJet Flight 592 was the most challenging one they had ever encountered up until that time.

Enlarge this image
Flight 111

Thousands of fragments from Swissair Flight 111 were collected as part of the crash inquiry and held in a giant hangar, where investigators pored over them seeking clues to the disaster's cause.

Note: This article originally appeared, in slightly different form, on NOVA's Crash of Flight 111 Web site.

The Deadliest Plane Crash Home | Send Feedback | Image Credits | Support NOVA

© | Created September 2006