US officials have expressed confidence that Ibrahim al-Asiri, al Qa’ida’s master bombmaker, was killed by a CIA drone strike last year. Al-Asiri was known for having perfected miniaturized bombs with little to no metal content, making them difficult for screening processes to detect. He is believed to have been behind such high-profile plots as the “underwear bomb” attempt that intended to detonate a flight in 2009 and “the printer bomb” that involved planting explosive devices in printers sent from Yemen to the US. However, some terrorism experts have indicated their skepticism that he was in fact killed, noting that al Qa’ida has not released any statement acknowledging his death, which is a normal practice for the group. And even if he is dead, it is unlikely that his expertise has died with him. Officials believe he trained a number of apprentices and that his tradecraft was exported to other terrorist groups. CNN.