The CIA and its overseas partners thwarted the attack following a covert Yemeni intelligence operation. Those behind the plot apparently hoped to take down a plane, but U.S. officials revealed Tuesday that the would-be bomber at the heart of the plot was actually an informant working for the CIA and Saudi Arabian intelligence.
The plot was foiled at around the same time as last week's first anniversary of Osama bin Laden's death at the hands of navy SEALs last year, but contrary to initial reports, it was not timed to coincide with the anniversary.
The bomb was non-metallic and wouldn't have been detected by airport screening devices, officials say, but likely would have been picked up by body scanners. There were no changes planned for airport security measures in the U.S. as a result of the plot.
The device, seized somewhere outside Yemen in the Middle East, was an upgraded version of the so-called underwear bomb used in a failed al-Qaida jetliner bombing on Christmas Day in 2009. The Associated Press reported late Tuesday it contained the chemical lead azide, a compound that wasn't used in the Christmas bomb.
The new bomb never made it onto the plane targeted for the attack, and the would-be bomber is "no longer a threat," John Brennan, President Barack Obama's counterterrorism adviser, said earlier Tuesday on NBC's "Today" show.
"We're continuing to investigate who might have been associated with the construction of it as well as plans to carry out an attack," he said.
"And so we're confident that this device and any individual that might have been designed to use it are no longer a threat to the American people."
Obama was briefed about the plot in early April, the White House said. The AP learned of the plot last week, but only broke the story late Monday after abiding by administration requests not to publish for several days due to security concerns.
A week after congressional Republicans maligned the president for "politicizing" the bin Laden anniversary, they were quick to suggest news of the foiled plot had been leaked to the AP prematurely and "promoted" for political gain.
"In this town, in a political season, people need to be a little more cautious — actually they need to be a lot more cautious — about how they promote this information at a time when it might not be most beneficial to the intelligence committee to do it," Mike Rogers, the head of the House of Representatives committee, said on CNN.
The Michigan congressman said he'll "be asking some pretty hard questions" about the timing of the released information.
"I just know that in a political season, funny things happen," he said.
He added that a congressional hearing could be necessary to probe any possible leak.
"If something bad happens because it was leaked too early, that's a catastrophe," he said. "We need to be really careful about this kind of thing."
Pete King, the head of the House's homeland security committee, stopped short of suggesting the leak was politically motivated but added: "Something with the timing here raises questions."
Republicans spent last week griping that Obama was taking too much credit for bin Laden's death just seven months before November's presidential election. That didn't seem to be the case in the early hours, anyway, of yet another national security triumph for his administration.
On a campaign-style swing to Albany, N.Y., on Tuesday, Obama didn't address the foiled plot.
"I will say that he's certainly pleased with the success of our intelligence and counterterrorism officials in foiling the attempt by al-Qaida to use this explosive device," said White House press secretary Jay Carney.
"It is indicative of the kind of work that our intelligence and counterterrorism services are performing regularly to counter the threat posed by al-Qaida."
Obama's re-election team used the occasion of last week's bin Laden anniversary to herald the president's decision to authorize the raid on the 9-11 mastermind's Pakistani hideout last May.
In an ad featuring former president Bill Clinton lauding Obama's courage, there was also a suggestion that Republican front-runner Mitt Romney would not have made the same call.
Republicans cried foul, accusing Obama of playing crass politics over an event that should have united Americans. Romney, for his part, essentially said the decision to go after bin Laden was a no-brainer.
The sniping continues this week, with a former member of the Joint Chiefs of Staff accusing Obama of dithering for more than a year over the raid.
"My sources tell me that the White House was trying to verify that the target was actually there, as opposed to just rely on circumstantial evidence," retired Gen. Jack Keane told Fox News over the weekend.
"They actually wanted a photo, they wanted to see him, that he was really there, and without that there was a lot of delay and procrastination about it because they wanted verification."
He added that U.S. forces "actually had the target the summer before execution ... and it took until the following May to execute the mission."