The following outline is provided as an overview of and topical guide to the September 11 attacks and their consequences: The September 11 attacks were four coordinated suicide attacks upon the United States in New York City and the Washington, D.C., area on September 11, 2001. On that Tuesday morning, 19 terrorists from the Islamist militant group al-Qaeda hijacked four passenger jets. The hijackers intentionally crashed two planes, American Airlines Flight 11 and United Airlines Flight 175, into the Twin Towers of the World Trade Center in New York City; both towers collapsed within two hours. Hijackers crashed American Airlines Flight 77 into the Pentagon in Arlington, Virginia. The fourth jet, United Airlines Flight 93, crashed into a field near Shanksville, Pennsylvania, after passeng