He doesn't do any ariel stunts. We haven't seen him hang gliding, sky diving, rappelling out of a helicopter (or waterskiiing behind one) or piloting a plane or hot air balloon. He's prejudiced against pilots, or has a fear of heights? Maybe he wants to show he's as brave, confident and virile as president Bush without looking like he's competing?
On the contrary, Kerry has bragged a great deal about being a pilot. He recently claimed to have taken the controls and done amazing acorbatic stunts while on a tour in an Israeli fighter jet years ago.
Also, Kerry claimed to have been flying the helicopter that he used during the Iowa primary. No one in the media bothered to point out that helicopters and planes are completely different ballgames. Just because you can fly a Cessna, doesn't mean you can jump behind the controls of a helicopter.