September 11 attacks
The September 11 attacks (also referred to as 9/11) were a series of four coordinated terrorist attacks by the Islamic terrorist group al-Qaeda against the United States on the morning of Tuesday, September 11, 2001. The attacks killed 2,996 people, injured over 6,000 others, and caused at least $10 billion in infrastructure and property damage. Additional people died of 9/11-related cancer and respiratory diseases in the months and years following the attacks.
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.