A drone missile strike in Shabwa, Yemen, on Sunday killed a man named Fahd Mohammad Ahmed Al-Quso, the Yemeni government said in a statement.

Al-Quso, 37, from Yemen, was best known in the United States for heading terrorist operations in the USS Cole bombing, which killed 17 American sailors in 2000. More recently, Al-Quso had replaced Anwar al Awlaki as head of external operations for Al Qaeda in the Arabian Peninsula.

He was continuing the terrorist group's plans to take down an international airliner with an explosive - one foiled in recent days, government officials say.

A previous attempt, with a bomb made by AQAP bomb-maker Ibrahim Hassan al-Asiri, had failed on Christmas Day 2009, when the bomber, Umar Faruq Abdulmuttalab, failed to detonate the device that had been hidden in his underwear.

U.S. government sources tell ABC News that Al-Quso and Asiri continued to plan for a similar terrorist attack, using a small IED that could be hidden on a person, with the same goal of bringing down an international airline.

In April, their plot, based in Yemen, was detected by intelligence sources. American and other intelligence agencies were, sources said, on top of the plot from the beginning and closely monitoring it. Early last month White House counterterrorism czar John Brennan told President Obama about the plot.

Senior administration officials say their understanding is that this was not a plot tied to the anniversary of the death of Osama bin Laden, that this was just a coincidence of timing. U.S. intelligence sources assess the threat from AQAP is growing "due to the territorial gains the group made during the political standoff in Yemen that lasted from early 2011 until this past February, a government official says. "Those territorial gains have allowed the group to establish additional training camps."

"We were aware of the plot throughout its development," a senior administration source tells ABC News. "So we never thought Americans were at risk. They never got to the point where they were close to putting it on a plane."

For this reason, Brennan would give Obama regular updates on the plot and the attempt to stop it, but there was never any need to hold an emergency meeting.

The IED was on its way to the individual who would carry out the operation when it was intercepted by law enforcement forces.

"It could have been a device used to bring down an airplane," a counterterrorism source tells ABC News.

"The device has the hallmarks of previous AQAP bombs that the group used in the failed assassination attempt on Saudi security official Mohammed Bin Nayif and that it used in the failed 2009 Christmas Day bombing," the government official said. "The device, like those earlier devices, is non-metallic."

A preliminary review indicates that it has some significant differences from Abdulmuttalab's device, the third official said.

"It is clear that AQAP is revamping its bomb techniques to try to avoid the causes of the failure of the 2009 device," that official said. "We are confident that the study of the device will yield valuable insights that will aid us in adapting security practices and counterterrorism operations here and abroad."

The IED is in the hands of the FBI and is, according to sources, being thoroughly examined.