Four planes were hijacked on September 11, 2001, with 19 terrorists crashing two planes into the World Trade Center towers, one into the Pentagon, and one crashing in Pennsylvania, resulting in over 3000 casualties. The first plane struck the North Tower of the World Trade Center at 8:46 am, and the second plane hit the South Tower at 9:03 am. Both towers collapsed after being struck. Flight 77 then crashed into the Pentagon at 10:07 am with no survivors. The terrorist group Al-Qaeda, headed by Osama bin Laden, took responsibility for coordinating the 9/11 attacks on the United States.