The Twin Towers of the World Trade Center fell on September 11, 2001. The South Tower collapsed at 9:59 a.m. after being hit by United Airlines Flight 175 at 9:03 a.m., and the North Tower collapsed at 10:28 a.m. after being hit by American Airlines Flight 11 at 8:46 a.m. Both towers were destroyed as a result of terrorist attacks carried out by al-Qaeda