Al-Qaeda executed the September 11 attacks.
Al-Qaeda . Al-Qaeda has mounted attacks on civilian and military targets in various countries , including the 1998 U.S. embassy bombings , the September 11 attacks , and the 2002 Bali bombings . September 11 attacks . were a series of four coordinated terrorist attacks by the Islamic terrorist group al-Qaeda on the United States on the morning of Tuesday , September 11 , 2001 . Suspicion for the attack quickly fell on al-Qaeda . United Airlines Flight 93 was a domestic scheduled passenger flight that was hijacked by four Al-Qaeda terrorists on board , as part of the September 11 attacks .