The sourcing here is a bit uncertain, but this is a great rumor, and it may be true. Let it all come out in the wash.
“Contrary to some news reports that suggest Killian admired Bush, Linke says the officer didn’t have much use for the young Lieutenant. He mentioned that Bush appeared to have a drinking problem, she recalls, but he was most offended by another incapacity: his fear of flying. According to Linke, Killian said Bush was grounded in his fourth year of flying after he became incapable of flying or properly landing a plane.”
PS. Dave already posted this, but I thought the Erica Jong reference was worth keeping.
UPDATE: Maybe he was afraid to fly because he was no good at it.