A global search for accomplices in the Detroit airliner plot is under way after an Al Qaeda group based in Yemen claimed responsibility for the operation and the would-be bomber was reported to have said that more attacks were being planned. Al Qaeda in the Arabian Peninsula, a terrorist cell led by a former personal secretary to Usama bin Laden, issued a statement saying that the failed attack by Umar Farouk Abdulmutallab was a response to American-backed airstrikes on the group in Yemen this month.