World Trade Center site
On the morning of September 11, 2001, Islamic terrorists affiliated with Al-Qaeda hijacked American Airlines Flight 11 and United Airlines Flight 175, both which were en route to Los Angeles, and intentionally crashed them into the two main towers of the World Trade Center. The towers collapsed within two hours of the collisions. 2,606 people, including 2,192 civilians, 71 law enforcement officers, and 343 firefighters, who were in the towers and in the surrounding area died in the attacks, as well as 147 civilians and the 10 hijackers aboard the two airliners. After the collapse of the World Trade Center, hospital workers and law enforcement officers began referring to the World Trade Center site as "Ground Zero".
Aircraft hijacking
On September 11, 2001, 19 al-Qaeda Islamic extremists hijacked American Airlines Flight 11, United Airlines Flight 175, American Airlines Flight 77, and United Airlines Flight 93 and crashed them into the Twin Towers of the World Trade Center, the southwestern side of the Pentagon, and Stonycreek Township near Shanksville, Pennsylvania (after passengers acted to stop the hijackers; its intended target was either the White House or the U.S. Capitol) in a terrorist attack. All in all, 2,996 people perished and more than 6,000 others were injured in the attacks. This casualty toll makes the hijackings the most fatal in history.