Confirmation of al-Asiri’s death to Fox News and the AP follows a United Nations report last week stating that the 36-year-old Saudi national may have been killed in the second half of 2017.

Al-Asiri is believed to have built the underwear bomb that a Nigerian man, Umar Farouk Abdulmutallab, tried to detonate on board a Northwest Airlines flight to Detroit from Amsterdam in December 2009. He is also behind a plot to place bombs hidden in printer cartridges on U.S.-bound cargo jets in 2010.

U.S. intelligence has believed that al-Asiri and his confederates were constantly working to improve their bomb designs so that they could get past airport security.