The events of 9/11 began on the morning of September 11, 2001, when four commercial passenger airliners were hijacked by 19 members of the Islamic terrorist group al-Qaeda. Two of the hijacked planes, American Airlines Flight 11 and United Airlines Flight 175, were flown into the North and South Towers of the WTC respectively. The impact of the planes and the resulting fires caused both towers to collapse within approximately two hours of being hit.
A third hijacked plane, American Airlines Flight 77, was flown into the Pentagon building in Arlington, Virginia, near Washington, D.C. The fourth hijacked plane, United Airlines Flight 93, crashed into a field in Stonycreek Township, Somerset County, Pennsylvania, after a struggle between the hijackers and passengers attempting to regain control of the plane.
These coordinated attacks against civilian targets on American soil resulted in the loss of almost 3,000 lives, including numerous civilians, emergency responders, and passengers on the hijacked planes, making it one of the deadliest terrorist attacks in history. The destruction of the World Trade Center buildings particularly became a powerful and iconic symbol of the terrorist acts performed on that day.