A US drone strike in Yemen killed Al Qaeda's chief bomb maker, Ibrahim Al Asiri, who was behind the 2009 Christmas Day plot to down an airliner over Detroit and other foiled aviation-related terror attacks, Yemeni officials and a tribal leader have confirmed.
The killing of Al Asiri deals a heavy blow to Al Qaeda's ability to strike western targets and piles pressure on the group that lost some of its top cadres over the past years in similar strikes.
A Yemeni security official confirmed Al Asiri was dead, while a tribal leader and an Al Qaeda-linked source said he was killed in a US drone strike in the eastern Yemeni province of Marib.
The tribal leader said that Al Asiri was struck, along with two or four of his associates, as he stood beside his car.
Al Qaeda has not commented on Al Asiri's death. Instead of the typical "eulogies" on militant websites, the Yemeni source said the group was trying to hunt down suspected "spies" who might have tipped off the US on his whereabouts.
The confirmation of Al Asiri's death follows a UN report this week saying that the 36-year-old Saudi national, who is on the US list of most wanted militants, may have been killed in the second half of last year.
Al Asiri is believed to have built the underwear bomb that a Nigerian man, Umar Farouk Abdulmutallab, tried to detonate on a passenger jet over Detroit in December 2009. He was also behind bombs hidden in printer cartridges placed on US-bound cargo jets in 2010.
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US intelligence over the past years believed that Al Asiri and his confederates were constantly working to improve their bomb designs so that they could get past airport security.
In July 2014, the US banned uncharged mobile phones and laptops aboard flights arriving from Europe and the Middle East.
Al Asiri, who studied chemistry in the Saudi capital of Riyadh, even once placed explosives inside his younger brother's clothes in a plot to assassinate the then Saudi interior minister, Mohammed bin Nayef, in 2009. The brother, Abdullah, died in the explosion while the top US counterterrorism ally was slightly wounded.
The US has long viewed Al Qaeda's Yemeni branch as its most dangerous affiliate, in part because of Al Asiri's expertise in explosives. Since 2014, the US has offered $5 million (Dh18m) for information leading to his capture. He is thought to have escaped death many times in US drone strikes in Yemen.
Al Asiri's last known statement was a 2016 audio message threatening Saudi Arabia and the US after the kingdom executed 47 Al Qaeda suspects.
Wanted by the US, Saudi Arabia and Interpol, Al Asiri fled Saudi Arabia for Yemen, along with other extremist militants escaping a crackdown in the kingdom.
Once in Yemen, they merged with local Al Qaeda militants who escaped from a Yemeni prison in 2006 to form Al Qaeda in the Arabian Peninsula, or AQAP.
Since 2015, Al Qaeda has exploited the turmoil of Yemen's civil war between Iran-backed Houthi rebels and government forces supported by the Saudi-led Arab Coalition. Amid the chaos, AQAP expanded its territory, occupied entire cities, looted security camps, banks and collected taxes from locals.
The UN report on Monday, which first raised allegations that Al Asiri may have been killed, also said that Al Qaeda's global network "continues to show resilience", with its affiliates and allies much stronger than ISIS in some places, including Somalia, Yemen, South Asia and Africa's Sahel region.
It added that Yemen's lack of a strong central government "has provided a fertile environment for" AQAP's expansion and estimated its strength inside Yemen at between 6,000 and 7,000 fighters — compared to between only 250 to 500 ISIS fighters.
Al Qaeda's top havens in Yemen are in the central Bayda and eastern Marib provinces. But since 2015, it has suffered heavy losses in leadership as US drone strikes killed off top cadres, including co-founder Nasser Al Wahishi, who was Osama bin Laden's top aide. Veteran Al Qaeda leader Qassim Al Rimi succeeded Al Wahishi.