The St. Petersburg Times comes up with the story on three Saudi nationals that did a lot of flying around the country… on 13 Sept 2001, when commercial aviation was all still grounded. As the story says:
“They got the approval somewhere,” [Manuel Perez, a retired FBI agent who accompanied the Saudis on the flight,] is quoted as telling [Author Craig Unger, who first disclosed the possibility of a post-9/11 Saudi airlift in his book House of Bush, House of Saud]. “It must have come from the highest levels of government.”
The “highest levels” had no comment, of course.