The 9/11 Commission, a US government commission established to investigate the attacks, found no evidence that bin Laden or al-Qaeda had prior knowledge of the specific details of the plot. However, the commission did conclude that bin Laden had provided general support to the hijackers, including financial assistance and training.
The attacks were carried out by 19 al-Qaeda hijackers, who hijacked four commercial airliners and crashed them into the World Trade Center towers, the Pentagon, and a field in Pennsylvania. The attacks resulted in the deaths of nearly 3,000 people and caused billions of dollars in damage.
Bin Laden was killed by US forces in a raid on his compound in Pakistan in 2011.