On September 11, 2001, 19 al-Qaeda terrorists hijacked 4 commercial jets and crashed 2 planes into the World Trade Center towers in New York City, a third plane into the Pentagon near Washington D.C., and a fourth plane crashed into a field in Pennsylvania. Over 3,000 people were killed in the 9/11 terrorist attacks, which triggered major U.S. counterterrorism initiatives and designated each September 11th as Patriot Day in memory of the victims.