On the morning of September 11, 2001, four commercial airliners were hijacked by nineteen terrorists in a coordinated attack. These planes were:
- American Airlines Flight 11, which was flown into the North Tower of the World Trade Center.
- United Airlines Flight 175, which was flown into the South Tower of the World Trade Center.
- American Airlines Flight 77, which crashed into the Pentagon.
- United Airlines Flight 93, which crashed into a field in Pennsylvania after passengers attempted to overcome the hijackers.
Thus, a total of four planes were hijacked that morning
