This is pretty funny stuff, however Shatner isn't the only sci fi guy with a fear of flying — when Issac Asimov was alive he was afraid to take airplane trips:
"Star Trek legend William Shatner has been offered a real-life space flight — but he won’t go boldly. Shatner — who plays fearless Kirk — says he is terrified of taking up Sir Richard Branson’s offer of joining Virgin Galactic’s first passenger flight in 2008. The actor fears he will throw up in space or the craft will crash. Shatner, 75, said yesterday: “I’m interested in man’s march into the unknown but to vomit in space is not my idea of a good time."
...however the article notes that Alien’s Sigourney Weaver is signed up!