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It would become a signature element of al-Asiri’s plots, according to intelligence analysts.

After the failed Christmas 2009 bombing, investigators pulled al-Asiri’s fingerprint off the bomb hidden in the underwear of the Nigerian-born suspect, Umar Farouk Abdulmutallab, aboard the Northwest Airlines flight.

Less than a year later, al-Asiri was linked to the discovery of printer cartridges packed with PETN and sent by international courier with Chicago-area synagogues listed as the destination. The explosive-rigged packages — believed powerful enough to bring down a plane — were pulled off airplanes in England and the United Arab Emirates.

Al-Asiri became a major focus of America’s anti-terrorism efforts. In March 2011, Washington officially designed al-Asiri as a wanted terrorist, calling him the primary bombmaker for AQAP. It also presumably puts al-Asiri among the chief targets on the U.S. hit list.

Last month, U.S. officials expressed concern that al Qaeda “intends to advance plots along multiple fronts, including renewed efforts to target Western aviation,” according to a joint intelligence bulletin circulated from the U.S. Northern Command, the FBI and Homeland Security Department.

While al-Asiri has been dubbed the master bomb-maker of al Qaeda’s Yemen franchise, it may be wrong to label him the linchpin of the group’s ability to strike with explosives, said Gregory Johnsen, a Yemen expert at Princeton University.

“I think it is safe to assume that in the nearly six years that he has been in Yemen, he has trained other individuals to replace him if he were to be killed,” Johnsen wrote on his blog Tuesday. “It is unlikely that Asiri is the only bombmaker AQAP has within its ranks — he is just the only name we know.”