I think you should try different phobia type training so instead he enjoys the flight experience. The only way he can overcome it is by accepting the whole experience. If you try to stop it then it will get worse. Just think "Whatever will be, will be". The thing with flying is usually people don't wanna feel out of control, but the irony of it is is that it ends up controlling you.
I had my first flight last week. Once your in the air for a long time u just get bored of caring.