Acutally, the Saudis flew out on 9/13, I think...and air travel HAD resumed for most folks by then. This is a fact clarified in a USA Today article, even by Moore's co-producer. They admitted the facts were blurred a bit here. This, to me, is not the issue, though, that they were allowed to fly before other people, but that they were allowed to fly AT ALL without being questioned by the FBI.
The Bush family's ties to Saudis and oil interests and the fact that dumb, desperate working class people are actively recruited for the military are the most compelling things in the film that I saw, and those ARE facts.