On the morning of September 11, 2001, the deadliest terrorist attack in U.S. history took place when four commercial airliners were hijacked by members of the Islamic extremist group al-Qaeda. The first two planes, American Airlines Flight 11 and United Airlines Flight 175, were flown into the two towers of the World Trade Center in New York City. A third plane, American Airlines Flight 77, hit the western side of the Pentagon, just outside Washington, D.C. The fourth hijacked plane, United Airlines Flight 93, crashed down in a field in rural Pennsylvania, never reaching its intended target because its crew and passengers fought back against the terrorists. Nearly 3,000 people lost their lives during the 9/11 attacks, a number that would almost certainly have been significantly higher if not for the actions of those aboard Flight 93.