“The Saudi embassy contacted the FBI about possibly evacuating some Saudi nationals, fearing reprisal attacks; the FBI prescreened the Saudi nationals, including the members of the Bin Ladin family before permitting them to leave, and many were interviewed; [counterterrorism czar] Richard Clarke approved the departure of the planes only after he had been told that the FBI had reviewed the passengers to its satisfaction; and none of the planes departed the United States before September 14, 2001, when U.S. airspace was reopened.”
– Thomas Kean and Lee Hamilton, Without Precedent, Page 255