Organizers of the September 11 attacks

The hijackers in the September 11 attacks were 19 men affiliated with al-Qaeda. Fifteen of the 19 were citizens of Saudi Arabia, and the others were from the United Arab Emirates (2), Egypt, and Lebanon. The hijackers were organized into four teams, each led by a pilot-trained hijacker with three or four "muscle hijackers," who were trained to help subdue the pilots, passengers, and crew.

The first hijackers to arrive in the United States were Khalid al-Mihdhar and Nawaf al-Hazmi, who settled in San Diego County, California, in January 2000. They were followed by three hijacker-pilots, Mohamed Atta, Marwan al-Shehhi, and Ziad Jarrah in mid-2000 to undertake flight training in south Florida. The fourth hijacker-pilot, Hani Hanjour, arrived in San Diego in December 2000. The rest of the "muscle hijackers" arrived in early- and mid-2001.

The 2001 attacks were preceded by the less well known Bojinka plot which was planned in the Philippines by Ramzi Yousef (of the 1993 World Trade Center bombing) and Khalid Shaikh Mohammed. Its objective was to blow up twelve airliners and their approximately 4,000 passengers as they flew from Asia to the United States. The plan included crashing a plane into the CIA headquarters, lending credence to the theory that Khalid Shaikh Mohammed evolved this plot into the September 11 attacks. The plot was disrupted in January 1995 after a chemical fire drew the Filipino police and investigation authorities' attention, resulting in the arrest of one terrorist and seizure of a laptop containing the plans. One person was killed in the course of the plot — a Japanese passenger seated near a nitroglycerin bomb on Philippine Airlines Flight 434. The money handed down to the plotters originated from Al-Qaeda, the international Islamic jihadi organization then based in Sudan.

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