Britannica AI Icon
Adding us as a Preferred Source tells Google you trust our content, so our articles show up more often in your Google Search, Discover feed, and AI Overviews.
verifiedCite
While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions.
Select Citation Style
Feedback
Corrections? Updates? Omissions? Let us know if you have suggestions to improve this article (requires login).
Thank you for your feedback

Our editors will review what you’ve submitted and determine whether to revise the article.

External Websites

The September 11 attacks were a series of airplane hijackings and suicide attacks committed in 2001 by 19 terrorists associated with the Islamic extremist group al-Qaeda. It was the deadliest terrorist attack on U.S. soil; nearly 3,000 people were killed. The attacks involved the hijacking of four planes, three of which were used to strike significant U.S. sites. American Airlines flight 11 and United Airlines flight 175 were flown into the World Trade Center’s north and south towers, respectively, and American Airlines flight 77 hit the Pentagon. United Airlines flight 93 crashed in a field near Shanksville, Pennsylvania, after passengers attempted to overpower the hijackers. The plane was believed to be headed to the U.S. Capitol building in Washington, D.C.

See our article on the September 11 attacks for a fuller discussion of the events of the day and their aftermath.

The Editors of Encyclopaedia BritannicaThis article was most recently revised and updated by Mindy Johnston.
Discover the fascinating events that shaped the world, straight from our editors.
By clicking “Sign Up”, you consent to the Britannica Privacy Policy and Terms of Use.