The term "9/11" refers to the terrorist attacks that occurred on September 11, 2001, in the United States. On that day, 19 terrorists hijacked four commercial airplanes in a coordinated attack by the Islamist extremist group al-Qaeda. Two planes were flown into the Twin Towers of the World Trade Center in New York City, causing both towers to collapse. A third plane crashed into the Pentagon in Arlington, Virginia, and the fourth plane, United Airlines Flight 93, crashed into a field in Pennsylvania after passengers attempted to regain control from the hijackers
. These attacks resulted in the deaths of nearly 3,000 people, making it the deadliest terrorist attack in history. The victims included civilians, first responders, and military personnel. The attacks led to significant changes in U.S. and global security policies, including the launch of the global War on Terror
. The attacks were meticulously planned and executed, with the hijackers targeting iconic U.S. landmarks to maximize impact and casualties. The event is commemorated by the National September 11 Memorial & Museum, which preserves the history and honors the victims and responders
. In summary, 9/11 was a series of four coordinated terrorist suicide attacks by al-Qaeda on U.S. soil on September 11, 2001, resulting in massive loss of life and profound global consequences
