Responsibility for the September 11 attacks

Two weeks after the September 11 attacks, the Federal Bureau of Investigation connected the hijackers to al-Qaeda, a global, decentralized terrorist network. In a number of video, audio, interview and printed statements, senior members of al-Qaeda have also asserted responsibility for organizing the September 11 attacks. It is believed that Osama Bin Laden, Khalid Sheikh Mohammed, and Mohammed Atef were the ones who plotted the attacks after meeting together in 1999. It is also believed Khalid Sheikh Mohammed was the one who planned the attacks and that Atef was the one who organized the hijackers.

The FBI investigation into the attacks, codenamed operation PENTTBOM, was able to identify the 19 hijackers within days, as they made little effort to conceal their names on flight, credit card, and other records. By checking flight manifests and comparing them with other information, like watch lists, customs officials were able to find the names of all 19 hijackers quickly.

Passengers and crew aboard the flights provided information about the hijackers while the hijacking was in progress. Two flight attendants on American Airlines Flight 11, Betty Ong and Madeline Amy Sweeney, contacted airline personnel on the ground. Sweeney provided the seat numbers of the hijackers, and descriptions of the men, identifying Mohamed Atta as one of the hijackers. A flight attendant on United Airlines Flight 175 called a United Airlines mechanic and reported that hijackers had killed the crew. While the hijacking was in progress on American Airlines Flight 77, several passengers, including a flight attendant, Renee May, contacted and reported details of the hijacking to persons on the ground. Sales clerks identified two individuals to whom they sold tickets on Flight 77 as the hijackers Hani Hanjour and Majed Moqed. During the hijacking of United Airlines Flight 93, Jeremy Glick identified the hijackers as Arabic-looking and carrying box-cutters.

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