On September 11, 2001, the United States was subjected to a series of four coordinated terrorist attacks by the Islamic extremist group al-Qaeda. Nineteen terrorists hijacked four commercial airliners. Two of the planes were flown into the twin towers of the World Trade Center complex in New York City, causing both 110-story skyscrapers to collapse. A third plane was crashed into the Pentagon, the headquarters of the U.S. Department of Defense, in Arlington, Virginia. The fourth plane, initially targeting a location in Washington, D.C., crashed into a field in Shanksville, Pennsylvania, after its passengers and crew attempted to regain control from the hijackers.
The attacks began at 8:46 a.m. Eastern Daylight Time when American Airlines Flight 11 struck the North Tower of the World Trade Center. At 9:03 a.m., United Airlines Flight 175 hit the South Tower. The subsequent fires caused catastrophic structural failure, leading to the collapse of the South Tower at 9:59 a.m. and the North Tower at 10:28 a.m. At 9:37 a.m., American Airlines Flight 77 crashed into the western facade of the Pentagon. The final aircraft, United Airlines Flight 93, crashed in Pennsylvania at 10:03 a.m. Evidence from the cockpit voice recorder indicated a passenger revolt prevented the hijackers from reaching their intended target, believed to be either the U.S. Capitol or the White House.
The immediate aftermath included an unprecedented shutdown of U.S. airspace and the initiation of large-scale rescue and recovery operations. The attacks resulted in 2,977 fatalities, making it the deadliest terrorist act in world history. The long-term consequences were profound, fundamentally reshaping American foreign policy and domestic security. The events directly led to the U.S. launching the "War on Terror," which included the 2001 invasion of Afghanistan to depose the Taliban for harboring al-Qaeda. Domestically, the U.S. Congress passed legislation that created the Department of Homeland Security and enacted the USA PATRIOT Act, expanding government surveillance powers. Global airport security measures were drastically increased and remain in effect.
