The September 11 attacks, often referred to as September 11, were a series of four coordinated attacks by the militant Islamic terrorist group Al-Qaeda against the United States of America on the morning of Tuesday, September 11, 2001.
That morning, four commercial planes traveling from the northeastern United States to California were hijacked in flight by 19 al-Qaeda terrorists. The kidnappers were organized into three groups of five kidnappers and one group of four. Each group had a hijacker who received flight training and took control of the aircraft. Its explicit objective was to use each plane as a missile against a prominent American building, causing mass deaths and partial or complete destruction of targeted buildings.
The first plane to hit its target was American Airlines Flight 11. It was released in the North Tower of the World Trade Center complex in Lower Manhattan at 8:46 am. Seventeen minutes later, at 9:03 am, the South Tower of the World Trade Center was hit by United Airlines Flight 175. Both 110-story towers collapsed after an hour and forty-two minutes, leading to the collapse of other World Trade Center structures, including 7 World Trade Center and significantly damaged surrounding buildings.
A third flight, American Airlines Flight 77, flown from Dulles International Airport, was hijacked over Ohio. At 9:37 am, it collided with the west side of the Pentagon (the headquarters of the US military) in Arlington County, Virginia, causing the building’s side to partially collapse.
The fourth and final flight, United Airlines Flight 93, was to Washington, DC Passengers on the plane tried to regain control of the aircraft by fighting hijackers and ultimately diverted the flight from its intended target; he crashed in a field near Shanksville, Pennsylvania, at 10:03 am. Investigators determined that the target of Flight 93 was the White House or the US Capitol.
Immediately after the attacks, suspicion quickly fell on al-Qaeda. The United States formally responded by launching the War on Terror and invading Afghanistan to depose the Taliban, which failed to comply with US demands to expel al-Qaeda from Afghanistan and extradite al-Qaeda leader Osama bin Laden. Bin Laden escaped to the White Mountains, where he was attacked by US-led forces, but managed to escape.
Although bin Laden initially denied any involvement, in 2004 he formally claimed responsibility for the attacks. Al-Qaeda and bin Laden cited US support for Israel, the presence of US troops in Saudi Arabia and sanctions against Iraq as reasons. After evading capture for nearly a decade, bin Laden was located in a hideout in Abbottabad, Pakistan, and later killed during Operation Neptune Spear.
The destruction of the World Trade Center and nearby infrastructure seriously damaged New York City’s economy and created a global economic recession. Many countries have strengthened their anti-terrorism legislation and expanded the powers of law enforcement and intelligence agencies to prevent terrorist attacks.
US and Canadian civil airspace was closed until Sept. 13, while Wall Street trade was closed until Sept. 17. Many closures, evacuations and cancellations followed, out of respect or fear of further attacks. Cleanup of the World Trade Center site was completed in May 2002 and the Pentagon was repaired within a year. Construction on the replacement World Trade Center complex began in November 2006, and the building opened in November 2014.
The attacks resulted in 2,977 deaths, more than 25,000 injuries and substantial long-term health consequences, in addition to at least $10 billion in infrastructure and property damage. It remains the deadliest terrorist attack in human history and the single deadliest incident for firefighters and police in US history, with 340 and 72 dead respectively. Numerous memorials have been built, including the 9/11 Memorial & National Museum in New York City, the Pentagon Memorial in Arlington County, Virginia, and the National Flight 93 Memorial at the crash site in Pennsylvania.