PENTTBOM is the codename for the Federal Bureau of Investigation's probe into the September 11, 2001 attacks on New York City and Washington, D.C., the largest criminal inquiry in United States history. Its name stands for 'Pentagon/Twin Towers Bombing Investigation'. The investigation was launched on September 11, 2001 and involved 7,000 of the FBI's then 11,000 special agents.
Identifying the hijackers 
Identical letters 
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."
Passports recovered 
According to testimony by Susan Ginsberg, a staff member of the National Commission on Terrorist attacks upon the United States, in the January 26, 2004 Public Hearing:
- "Four of the hijackers' passports have survived in whole or in part. Two were recovered from the crash site of United Airlines flight 93 in Pennsylvania. These are the passports of Ziad Jarrah and Saeed al Ghamdi. One belonged to a hijacker on American Airlines flight 11. This is the passport of Satam al Suqami. A passerby picked it up and gave it to a NYPD detective shortly before the World Trade Center towers collapsed. A fourth passport was recovered from luggage that did not make it from a Portland flight to Boston on to the connecting flight which was American Airlines flight 11. This is the passport of Abdul Aziz al Omari."
- "In addition to these four, some digital copies of the hijackers passports were recovered in post-9/11 operations. Two of the passports that have survived, those of Satam al Suqami and Abdul Aziz al Omari, were clearly doctored. To avoid getting into classified detail, we will just state that these were manipulated in a fraudulent manner in ways that have been associated with al Qaeda."
WTC site 
Flight 93 
Atta's luggage 
The doctored passport of hijacker Abdulaziz Alomari was found in Mohamed Atta’s left-behind luggage.
When examining Mohamed Atta's left-behind luggage, the FBI found important clues about the hijackers and their plans. His luggage contained papers that revealed the identity of all 19 hijackers, and provided information about their plans, motives, and backgrounds. The FBI was able to determine details such as dates of birth, known and/or possible residences, visa status, and specific identity of the suspected pilots. None of these documents have been scrutinized by independent legal experts.
Linking the hijackers to al Qaeda 
The investigators were quickly able to link the 19 men to the terrorist organization al Qaeda, by accessing their intelligence agency files. The New York Times reported on September 12 that: "Authorities said they had also identified accomplices in several cities who had helped plan and execute Tuesday’s attacks. Officials said they knew who these people were and important biographical details about many of them. They prepared biographies of each identified member of the hijack teams, and began tracing the recent movements of the men." FBI agents in Florida investigating the hijackers quickly "descended on flight schools, neighborhoods and restaurants in pursuit of leads." At one flight school, "students said investigators were there within hours of Tuesday’s attacks." The Washington Post later reported that "In the hours after Tuesday’s bombings, investigators searched their files on [Satam] Al Suqami and [Ahmed] Alghamdi, noted the pair’s ties to [Nabil] al-Marabh and launched a hunt for him."
On September 27, 2001, the FBI released photos of the 19 hijackers, along with information about the possible nationalities and aliases of many.
On the day of the attacks, U.S. intelligence agencies also intercepted communications that pointed to Osama bin Laden. It was quickly asserted that Osama bin Laden was responsible for the attacks, and other suspects were ruled out. Although he denied the attacks at first, Osama bin Laden has purportedly admitted full and sole responsibility for the attacks in a video tape.
Press Releases 
- September 11, 2001: FBI opens investigations
- September 14: FBI releases list of 9/11 hijacker suspects
- September 27: FBI releases photographs of 9/11 hijacker suspects
- September 28: FBI releases four-page letter believed to be written by the hijackers
- October 4: FBI releases partial timeline for Boston-based hijackers
See also 
|Wikimedia Commons has media related to: Participants in the September 11 attacks|
- "Timeline of FBI History". Federal Bureau of Investigation.
- "Federal Bureau of Investigation - Facts and Figures 2003". Federal Bureau of Investigation.
- "FBI Releases Copy of Four-Page Letter Linked to Hijackers". FBI. 28 September 2001. Retrieved 11 September 2011.
- "Last words of a terrorist". The Observer. 30 September 2001. Retrieved 11 September 2011.
- "Federal Bureau of Investigation - Congressional Testimony". FBI. 3 October 2001. Retrieved 11 September 2011.
- Larry Neumeister (16 September 2001). "Suspected hijacker's passport found". Arizona Daily Star. The Associated Press. Retrieved 11 September 2011.
- Larry Neumeister (16 September 2001). "Passport of suspected hijacker found in debris". Las Vegas Review-Journal. The Associated Press. Retrieved 11 September 2011.
- "Seventh public hearing of the National Commission on Terrorist Attacks Upon the United States". The National Commission on Terrorist Attacks Upon the United States. 26 January 2004.
- Dorman, Michael (April 17, 2006). "Unraveling 9-11 was in the bags". Newsday (New York).
- Reaves, Jessica (January 2, 2002). "The Case Against Zacarias Moussaoui". Time.
- Canedy, Dana; Sanger, David E. (September 13, 2001). "After the attacks: The suspects; Hijacking Trail Leads F.B.I. to Florida Flight School". The New York Times. Retrieved May 22, 2010.
- John Mintz; Allan Lengel (21 September 2001). "FBI Arrests Kuwaiti Liquor Store Clerk". The Washington Post. Retrieved 11 September 2011.
- "The FBI Releases 19 Photographs of Individuals Believed to be the Hijackers of the Four Airliners that Crashed on September 11, 2001". FBI. 11 September 2001. Retrieved 11 September 2011.
- "Latest on the attacks on America, 7:00 p.m". CBS News. September 11, 2001.
- "Bin Laden "Confession" Video". YouTube. 16 February 2008.
- "Information Regarding September 11 Incidents". FBI. 11 September 2001. Retrieved 11 September 2011.
- "FBI Announces List of 19 Hijackers". FBI. 13 September 2001. Retrieved 11 September 2011.
- "Boston Division Seeks Assistance". FBI. 4 October 2001. Retrieved 11 September 2011.
- FBI's 9/11 Team Still Hard at Work from The Washington Post June 14, 2004
- FBI PENTTBOM suspects
- Translation of hijacker letters
- PENTTBOM timeline