The September 11 attacks (also referred to as September 11, September 11th, or 9/11) were a series of four suicide attacks that were committed in the United States on September 11, 2001, coordinated to strike areas of New York City and Washington, D.C. On that Tuesday morning, 19 terrorists from the Islamist militant group al-Qaeda hijacked four passenger jets. The hijackers intentionally piloted two of those planes, American Airlines Flight 11 and United Airlines Flight 175, into the North and South towers of the WorldTradeCenter complex in New York City; both towers collapsed within two hours. The hijackers also intentionally crashed American Airlines Flight 77 into the Pentagon in Arlington, Virginia, and intended to pilot the fourth hijacked jet, United Airlines Flight 93, into the United StatesCapitolBuilding in Washington, D.C.; however, the plane crashed into a field near Shanksville, Pennsylvania, after its passengers attempted to take control of the jet from the hijackers. Nearly 3,000 people died in the attacks, including the 246 civilians and 19 hijackers aboard the four planes.
Suspicion quickly fell on al-Qaeda, and in 2004, the group's leader, Osama bin Laden, who had initially denied involvement, claimed responsibility for the attacks. Al-Qaeda and bin Laden cited U.S. support of Israel, the presence of U.S. troops in Saudi Arabia, and sanctions against Iraq as motives for the attacks. The United States responded to the attacks by launching the War on Terror and invading Afghanistan to depose the Taliban, which had harbored al-Qaeda. Many countries strengthened their anti-terrorism legislation and expanded law enforcement powers. In May 2011, after years at large, bin Laden was located and killed.