2001 terror attacks in the U.S. The September 11 attacks, colloquially known as 9/11, were a coordinated series of suicide attacks perpetrated by the Islamic terrorist organization al-Qaeda against the United States in 2001. A total of 19 hijackers commandeered four commercial passenger airliners. The first two planes were flown into each of the Twin Towers at the World Trade Center in New York City, while the third plane crashed into the Pentagon, the headquarters of the United States Department of Defense, in Arlington County, Virginia. The fourth plane crashed in a rural field in Pennsylvania during a passenger revolt. 665,793 views on September 11, 2026 — Wikipedia's most-read article that day. Also most read: United Airlines Flight 93, Elena Rybakina, American Airlines Flight 11, Shailene Woodley. Wiki link