PENTTBOM

PENTTBOM is the codename for the Federal Bureau of Investigation's probe into the September 11 attacks of 2001, the largest criminal inquiry in the FBI's history. Its name stands for 'Pentagon/Twin Towers Bombing Investigation'. The investigation was launched on September 11, 2001, and involved 4,000 special agents and 3,000 professional employees.

The FBI was able to identify the 19 hijackers within a matter of days as few suspects made any effort to conceal their names on flight, credit card, and other records.

Three of the hijackers carried copies of an identical handwritten letter (in Arabic) that was found in three separate locations: the first, in a suitcase of hijacker Mohamed Atta that did not make the connection to American Airlines Flight 11 that crashed into the North Tower of the World Trade Center; the second, in a vehicle parked at Washington Dulles International Airport that belonged to hijacker Nawaf al-Hazmi; and the third at the crash site of United Airlines Flight 93 in Shanksville, Pennsylvania.

According to the testimony before the House Intelligence Subcommittee on Terrorism and Homeland Defense on October 3, 2001 given by J. T. Caruso—the Deputy Assistant Director of the FBI's Counterterrorism Division, "translations of the letter indicate an alarming willingness to die on the part of the hijackers."

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