An Al Qaeda suicide bomber dispatched from Yemen to down a passenger plane with military-grade explosives was actually a double-agent recruited by foreign intelligence services, reports have claimed.
The bomber, who has not been named, was sent by the Yemen branch of the terrorist group to blow up a jet bound for the United States via the United Arab Emirates.
The bomb, which was "undetectable" and contained no metal, had two detonators and was sewn into customised underwear. The Daily Mail said it was a more advanced version of a device with which bombers attempted to destroy a plane above Detroit on Christmas Day 2009.
The device would have "undoubtedly would have brought down an aircraft" according to an American official quoted in media reports.
The attack was reportedly scheduled to mark the first anniversary of the death of Al Qaeda leader Osama Bin Laden on 2 May.
But in what the New York Times has called an "extraordinary intelligence coup", the man was later revealed to in fact be working for the Saudi Arabian authorities and the CIA.
The London Times said that British officials were also involved, but added the security forces had declined to comment.
The bomber left Yemen last month before handing over the bomb, detailed plans for the attack and information on the leaders of the terrorist group, their locations and their future plots.
The information was not revealed to protect the agent and his family, officials have said.
According to the New York Times the bomb is now being analysed at its lab in Virginia to prevent future attacks and improve airport security.
The details provided by the agent led to a CIA-directed drone attack in Yemen which killed Yemeni Al Qaeda operations director Fahd Mohammed Ahmed Al-Quso, who was wanted for the bombing of the USS Cole in 2000.
Quso, who was 37, had a $5m bounty on his head according to CIA officials.
The American authorities said that they had been aware of the agent for several years, but that he was under the control of the Saudi government.
The story was first reported by the LA Times, apparently to the annoyance of American officials who claimed it might discourage governments from cooperating with the CIA in future.
Take a look at 10 other failed terrorist attempts, involving everything from shoe bombs to ricin, for another phew moment.