“The FBI had learned that Abu Zubaydah, a Saudi who had been chief of operations for Al Qaeda since 1996 and was in charge of training thousands of Muslim terrorists, was in touch with a Middle Eastern student at a flight school in Arizona. That alarming piece of information, however, was never forwarded to the White House. …On August 21 [2001], the CIA notified the Immigration and Naturalization Service (INS) that two other Al Qaeda operatives, [future 9/11 hijackers] Khalid Almidhar and Nawaf Alhazmi, should be put on the terrorist watch list.” The INS revealed to the FBI and CIA that “the two men had already entered the United States. …this astonishing revelation…was not forwarded to the White House or to Richard Clarke’s counterterrorism team.”
– Craig Unger, House of Bush, House of Saud, Pages 238-239