The first tower to collapse was the South Tower of the World Trade Center. It collapsed at 9:59 a.m. after being hit by United Airlines Flight 175 at 9:03 a.m. The North Tower, which was hit earlier at 8:46 a.m. by American Airlines Flight 11, collapsed later at 10:28 a.m. The South Tower collapsed first despite being struck second because the plane hit it at a lower floor and at a higher speed, causing more catastrophic structural damage and causing the tower to fail more quickly.
