Bomber in Plot on U.S. Airliner Said to Be a Double Agent WASHINGTON – The would-be suicide bomber dispatched by the Al Qaeda branch in Yemen last month to blow up a United States-bound airliner was actually a double agent who infiltrated the terrorist group and volunteered for the suicide mission, American and foreign officials said on Tuesday. In an extraordinary intelligence coup, the agent left Yemen, traveling by way of the United Arab Emirates, and delivered both the innovative bomb designed for his aviation attack and critical information on the group’s leaders to the C.I.A., Saudi and other foreign intelligence agencies. After spending weeks at the center of the terrorist network’s most dangerous affiliate, Al Qaeda in the Arabian Peninsula, the agent provided critical information that permitted the C.I.A. to direct the drone strike on Sunday that killed Fahd Mohammed Ahmed al-Quso, the group’s external operations director and a suspect in the bombing of the destroyer Cole in Yemen in 2000.