On the morning of September 11, 2001, Al-Qaeda-affiliated hijackers flew two Boeing 767 jets into the Twin Towers within minutes of each other; less than two hours later, both towers collapsed. The attacks killed 2,606 people in and within the vicinity of the towers, as well as all 157 on board the two aircraft. Falling debris from the towers, combined with fires that the debris initiated in several surrounding buildings, led to the partial or complete collapse of all the buildings in the complex, and caused catastrophic damage to ten other large structures in the surrounding area.