White House officials said President Obama was briefed on the plot in April by his counter-terror advisor, John Brennan.
Just one week ago, Brennan denied there was any such plot. "There is not credible reporting right now that there is an active plot underway to coincide with the anniversary of the bin Laden takedown," said Brennan then.
Last week, White House spokesman Jay Carney also denied the existence of a plot. "At this time we have no credible information that terrorist organizations including al Qaeda are plotting attacks in the U.S. to coincide with the anniversary of bin Laden's death," said Carney.
The chairman of the Senate Homeland Security Committee said the White House gave the misleading information for security reasons. Said Sen. Joe Lieberman, I-Connecticut, "I was told that no public announcement of the plot was made at the time in order to protect ongoing counter-terrorism operations in the field."
On Monday, a spokeswoman for the National Security Council said, "While the President was assured that the device did not pose a threat to the public, he directed the Department of Homeland Security and law enforcement and intelligence agencies to take whatever steps necessary to guard against this type of attack."
Security was stepped up at airports across Europe and in the U.S., in a bid to outwit AQAP's master bombmaker.
"We're dealing with a dynamic adversary here who bases their actions in part on our actions," explained Frank Cilluffo, director of the Homeland Security Policy Institute at George Washington University. "It's not static. So they're going to try to always identify the vulnerabilities and and the work-arounds in our own system."
Officials acknowledge that security standards at some European airports are much different.
Said Cilluffo, "Keep in mind this is overseas, we we also need to recognize that some of the standards that may be in place in the United States may not be met in other countries."
In the end, this latest plot was stopped not by technology, but by good spy work, with an apparent undercover spy work, with an apparent undercover operative inside al Qaeda.
Said Richard Clarke, "You have to wonder if this plot was blown by someone on the inside, whether or not that means the source is blown, and therefore they may no longer have someone on the inside, and would not know about the next plot."
U.S. officials say Fahd al-Quso, the head of operations for AQAP, was killed over the weekend by a U.S. drone strike. Asiri, the bombmaker, is still at large, and is believed to be training other bombmakers and making other bombs, all aimed at U.S. aircraft.