Al-Qaeda Launches Coordinated Attacks on U.S.
Nineteen hijackers affiliated with al-Qaeda seized four commercial airliners departing East Coast airports. Two struck the World Trade Center towers in New York, causing their collapse and killing nearly 3,000 people total. A third plane hit the Pentagon in Virginia, while passengers on the fourth overpowered the hijackers, forcing the aircraft down in a Pennsylvania field. The coordinated strikes represented the deadliest terrorist attack in history and the first major foreign assault on the U.S. mainland since 1812.
Why it matters: The attacks triggered immediate global military responses, including the invasion of Afghanistan, and led to sweeping changes in U.S. domestic security, aviation protocols, and foreign policy. They reshaped international alliances and counterterrorism strategies that persist today. Memorials at the three sites and annual remembrances continue to honor the victims.