The 9/11 attacks happened on the morning of September 11, 2001, when terrorists hijacked four US passenger planes. These hijackers deliberately crashed the planes into key targets: two planes hit the Twin Towers of the World Trade Center in New York, one struck the Pentagon near Washington, D.C., and the fourth plane crashed in Pennsylvania after passengers fought back, likely preventing an attack on the US Capitol or White House. Thousands of people were killed in these attacks, and the events led to significant consequences globally and within the US.

The hijackers were part of al Qaeda, a militant Islamic terrorist group led by Osama bin Laden. The attacks involved coordinated hijackings where the terrorists took control of the airplanes and used them as weapons. The first plane, American Airlines Flight 11, crashed into the North Tower, followed by United Airlines Flight 175 crashing into the South Tower. American Airlines Flight 77 hit the Pentagon, and United Airlines Flight 93 crashed in a field in Pennsylvania after passengers attempted to regain control.

Multiple factors contributed to the attack, including regional conditions in the Middle East, the rise of Islamic extremism influenced by historical events such as the Iranian Revolution and Soviet-Afghan war, anti-American sentiment fueled by US foreign policy, and intelligence failures that left the US vulnerable. The extremist group al Qaeda sought to inflict mass casualties and psychological impact on the US and its allies, which they achieved through this well-planned and coordinated attack.