WASHINGTON — U.S. officials are confident that al Qaeda's chief bomb maker Ibrahim al-Asiri has been killed by an American drone strike in Yemen. After Osama bin Laden was killed in 2011, al-Asiri might well have been the single most dangerous terrorist in the world.

"Probably the most sophisticated terrorist bomb maker on the planet. Incredibly creative, incredibly innovative," said former CIA deputy director Michael Morell.

This undated file photo released Oct. 31, 2010, by Saudi Arabia's Ministry of Interior purports to show Ibrahim Hassan al-Asiri. AP Photo/Saudi Arabia Ministry of Interior

Al-Asiri designed the so-called "underwear bomb," which nearly took down a U.S. airliner over Detroit on Christmas Day in 2009. The plot failed only because the young man wearing the bomb failed to detonate it properly.

One year later, the Saudi-born al-Asiri nearly pulled off another audacious attack by hiding explosive devices in printer cartridges being shipped on cargo planes to the United States. The devices got through airport security in London, and were only discovered because of a last-minute tip.

More recently, he was believed to be working on a bomb that could be hidden in a laptop or mobile device, leading the TSA to ban such items on some flight to the U.S.

"A good chunk of what you have to take out of your bag and what has to be screened is because of Asiri and his capabilities of putting explosives in very difficult to find places," Morell said.

The drone strike which the U.S. believes killed Asiri took place last year in Yemen. But his death does not end the threat since he taught his bomb making skills to other terrorists.