On September 11, 2001, four commercial airplanes were hijacked and crashed. American Airlines Flight 11, a Boeing 767, was the first to strike, hitting the North Tower of the World Trade Center at 8:46 a.m. Seventeen minutes later, at 9:03 a.m., United Airlines Flight 175, also a Boeing 767, crashed into the South Tower. The third aircraft, American Airlines Flight 77, a Boeing 757, was flown into the Pentagon in Arlington, Virginia, at 9:37 a.m. The final plane, United Airlines Flight 93, a Boeing 757, crashed into a field near Shanksville, Pennsylvania, at 10:03 a.m. after the passengers and crew fought back against the hijackers. In 2026, these four flight numbers are retired by their respective airlines and serve as somber markers of the lives lost. The 9/11 Memorial in New York continues to honor the 2,977 victims, including those on board the aircraft, ensuring their legacy is never forgotten in the history of aviation.