Answer:
The 9/11 attacks were a terrorist attack carried out in the United States by the terrorist group Al Qaeda, led by Osama Bin Laden, on September 11, 2001. In these attacks, 3 planes were hijacked and crashed in the two Twin Towers in New York and the Pentagon in Washington DC, while a fourth plane crashed in the open field in Pennsylvania.
These attacks, which caused the death of almost 3,000 people, were the most important attack in the history of the United States, generating a series of important consequences both nationally and internationally, being the starting point for the War on Terrorism and the sanction of the USA PATRIOT Act.