The 9/11 terrorist attacks occurred on September 11, 2001. On that morning, 19 Al Qaeda terrorists hijacked four commercial passenger planes in the United States. Two planes were flown into the Twin Towers of the World Trade Center in New York City, causing both towers to collapse. A third plane crashed into the Pentagon, near Washington, D.C., and a fourth plane crashed in rural Pennsylvania after passengers intervened to prevent it from reaching its intended target

. The attacks resulted in nearly 3,000 deaths and had a profound global impact. The event led to the U.S. declaration of the "War on Terror," the invasion of Afghanistan in October 2001, and later the invasion of Iraq. It also prompted many countries to introduce new anti-terrorism legislation

. Thus, the year when 9/11 happened is 2001.