September 11 attacks A collection of significant facts about the September 11 attacks. (more) What Were the September 11 Attacks? Ask the Chatbot a Question More Actions Share Share Share to social media Facebook X URL https://www.britannica.com/event/What-were-the-September-11-attacks Feedback Corrections? Updates? Omissions? Let us know if you have suggestions to improve this article (requires login). Feedback Type Select a type (Required) Factual Correction Spelling/Grammar Correction Link Correction Additional Information Other Your Feedback Submit Feedback Thank you for your feedback Our editors will review what you’ve submitted and determine whether to revise the article.

　　External Websites Ask the Chatbot a Question Written by The Editors of Encyclopaedia Britannica Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... The Editors of Encyclopaedia Britannica Last Updated: Sep 16, 2025 • Article History Table of Contents Table of Contents Ask the Chatbot 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 ...(100 of 141 words)

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