Details have emerged of how the CIA fooled al Qaida over the terror network's plot to bring down a plane with a nearly-undetectable bomb.
US intelligence learned last month that al Qaida's Yemen branch hoped to launch a spectacular attack using a new bomb aboard an airliner bound for America.
But the man the terrorists were counting on to carry out the attack was in fact working for the CIA and Saudi intelligence when he was given the bomb, US and Yemeni officials said, then turned the device over to authorities.
The dramatic sting operation thwarted the attack before it had a chance to succeed. The informant was now safely out of Yemen, officials said.
It was the latest misfire for al Qaida, which has repeatedly come close to detonating a bomb aboard a plane. For the United States, it was a victory that delivered the bomb intact to US intelligence.
The co-operation of the would-be bomber was first reported by The Los Angeles Times late on Tuesday night, but officials spoke anonymously about the operation.
The FBI is still analysing the explosive, which was intended to be concealed in a passenger's underwear. Officials said it was an upgrade over the bomb that failed to detonate on board a plane over Detroit, Michigan, on Christmas Day 2009.
The new bomb contained no metal and used a chemical - lead azide - that was to be a detonator in a nearly-successful 2010 plot to attack cargo planes, officials said.
Security procedures at US airports remained unchanged, a reflection of both the US confidence in its security systems and recognition that the government cannot realistically expect travellers to endure much more. Increased costs and delays to airlines and shipping companies could have a global economic impact, too.
"I would not expect any real changes for the travelling public," said House of Representatives Intelligence Committee chairman Mike Rogers. "There is a concern that overseas security doesn't match ours. That's an ongoing challenge."