Within minutes of the attacks, the Federal Bureau of Investigation opened the largest FBI investigation in United States history, operation PENTTBOM. The suspects were identified within 72 hours because few made any attempt to disguise their names on flight and credit card records. They were also among the few non-U.S. citizens and nearly the only passengers with Arabic names on their flights, enabling the FBI to identify them using such details as dates of birth, known or possible residences, visa status, and specific identification of the suspected pilots. On September 27, 2001, the FBI released photos of the 19 hijackers, along with information about many of their possible nationalities and aliases. The suspected hijackers were from Saudi Arabia (fifteen hijackers), United Arab Emirates (two hijackers), Lebanon (one hijacker) and Egypt (one hijacker).