The hijackers in the September 11 attacks were 19 men affiliated with Islamist jihadist organization al-Qaeda. They hailed from four countries; 15 of them were citizens of Saudi Arabia, two were from the United Arab Emirates, one was from Egypt, and one from Lebanon. To carry out the attacks, the hijackers were organized into four teams each led by a pilot-trained hijacker who would commandeer the flight with three or four "muscle hijackers" who were trained to help subdue the pilots, passengers, and crew. Each team was assigned to a different flight and given a unique target to crash their respective planes into. Mohamed Atta was the assigned ringleader over all 4 groups.

The September 11 attacks, commonly known as 9/11, were four coordinated Islamist suicide terrorist attacks carried out by al-Qaeda against the United States on September 11, 2001. That morning, 19 terrorists hijacked four commercial airliners scheduled to travel from the East Coast to California. The hijackers crashed the first two planes into the Twin Towers of the World Trade Center in New York City, two of the world's five tallest buildings at the time, and aimed the next two flights toward targets in or near Washington, D.C., in an attack on the nation's capital. The third team succeeded in striking the Pentagon, the headquarters of the U.S. Department of Defense in Arlington County, Virginia, while the fourth plane crashed in rural Pennsylvania during a passenger revolt. The September 11 attacks killed 2,977 people, making them the deadliest terrorist attack in history, and instigated the multi-decade global war on terror, fought in Afghanistan, Iraq, and elsewhere.