In Light of New Bomb Plot, U.S. Must Be 'Proactive,' Napolitano Says

GWEN IFILL: The latest conspiracy to attack commercial aviation in the U.S. yielded a low-key official response today, at least publicly.

Margaret Warner has the story.

MARGARET WARNER: It seemed business as usual at U.S. airports the day after news that the CIA foiled a new al-Qaida plot to bomb an airliner.

On ABC, White House Counterterrorism Adviser John Brennan led a chorus of U.S. officials seeking to reassure the public.

JOHN BRENNAN, U.S. deputy National Security adviser: I think people getting on a plane today should feel confident that their intelligence services are working day in and day out to stop these types of IEDs from getting anywhere near a plane.

MARGARET WARNER: Officials have said the recovered bomb containing no metal designed to fit inside underwear wouldn't have been detected by magnetometers. It's unclear if the new body scanners would have picked it up. The FBI is now analyzing the device.

JOHN BRENNAN: This IED was a threat from the standpoint of the design that we have been able to determine. And so now we're trying to make sure that we take the measures that we need to prevent any other type of IED, similarly constructed, from getting through security procedures.

MARGARET WARNER: There was no word on the fate of the would-be bomber, but at a Washington event with the NewsHour's Ray Suarez, Secretary of Homeland Security Janet Napolitano said the plot represents a clear challenge.

SECRETARY OF HOMELAND SECURITY JANET NAPOLITANO: And I think we have to acknowledge that our adversaries are very creative, and they are very determined, and they are very persistent. And that requires us to always be thinking proactively, not just reactively.

MARGARET WARNER: Authorities suspect the bomb was designed by Yemen-Ibrahim Hassan al-Asiri, the alleged designer of a cruder underwear bomb that failed to detonate on a jetliner over Detroit on Christmas Day, 2009, and devices found in printer cartridges seized in shipments from Yemen to the U.S. in 2010.

This latest plot underscored how al-Qaida in the Arabian Peninsula, AQAP, has gained ground in Yemen in the unrest that ousted President Ali Abdullah Saleh. The U.S. has responded with a stepped-up drone campaign that killed leading AQAP figure Anwar al-Awlaki last fall, and this past Sunday, a drone took out Fahd al-Quso, believed responsible for the bombing of the USS Cole in 2000.