The phrase "sep 11 attack 2001" functions as a proper noun phrase, designating a specific, historically significant event. It refers to a series of four coordinated terrorist attacks by the Islamic militant group al-Qaeda against the United States on the morning of Tuesday, September 11, 2001. The attacks resulted in 2,977 fatalities, over 25,000 injuries, and substantial long-term health consequences, in addition to at least $10 billion in infrastructure and property damage.
The attacks were executed by 19 al-Qaeda terrorists who hijacked four commercial airliners. Two of the planes, American Airlines Flight 11 and United Airlines Flight 175, were crashed into the North and South Towers, respectively, of the World Trade Center complex in New York City, leading to the collapse of both skyscrapers. A third plane, American Airlines Flight 77, was crashed into the Pentagon in Arlington, Virginia. The fourth plane, United Airlines Flight 93, crashed into a field in Shanksville, Pennsylvania, after passengers and crew attempted to overpower the hijackers; its intended target is believed to have been a federal government building in Washington, D.C., likely the U.S. Capitol or the White House.
The event triggered a profound and lasting impact on American society and global politics. In its immediate aftermath, the U.S. government launched the "War on Terror," which included the invasion of Afghanistan to depose the Taliban, who had harbored al-Qaeda. Domestically, it led to the passage of sweeping national security legislation, such as the USA PATRIOT Act, and the creation of the Department of Homeland Security. The attacks also fundamentally altered air travel security protocols worldwide, introducing measures that remain in place today.
