The September 11 attacks, often 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 September 11, 2001. The attacks involved the hijacking of four commercial airliners, which were then deliberately crashed into significant targets, causing immense destruction and loss of life.

The initial targets included the iconic World Trade Center complex in New York City, where two of the hijacked planes were flown into the North and South Towers, leading to their catastrophic collapse. A third plane was crashed into the Pentagon in Arlington, Virginia, causing a partial collapse of the building. The fourth plane, United Airlines Flight 93, was intended for another target in Washington, D.C., but crashed into a field in Shanksville, Pennsylvania, after passengers and crew members attempted to regain control from the hijackers.

These attacks resulted in the deaths of nearly 3,000 people, including over 2,600 in New York City, 125 at the Pentagon, and 40 in Pennsylvania. The event profoundly impacted global security policies, initiating the U.S. War on Terror and reshaping international relations. Across the provided sources, including Wikipedia, the National September 11 Memorial & Museum, and the National Archives, there is a consistent factual narrative regarding the perpetrators, the method of attack, the specific targets, and the immediate consequences, with no discernible disagreements in their historical accounts.