The September 11, 2001 attacks were orchestrated and carried out by the terrorist organization al-Qaeda, led by Osama bin Laden. The key operational planner was Khalid Sheikh Mohammed, who proposed the idea of using hijacked airplanes as weapons to attack the United States. Nineteen hijackers, mostly from Saudi Arabia and trained by al-Qaeda, executed the attacks by hijacking four planes, crashing them into the World Trade Center towers in New York City, the Pentagon in Virginia, and a field in Pennsylvania after passengers intervened
. Osama bin Laden initially denied involvement but later admitted responsibility in various statements and videos. The U.S. government and intelligence agencies quickly identified bin Laden and al-Qaeda as responsible, leading to the largest FBI investigation in history and subsequent military operations to capture bin Laden, who was killed in 2011
