Let him do what HE wants to do. It's his life, not yours. Did you do what your parents wanted, or become interested in what interested them?
It sounds like your kid's got a mind of his own, which at the age of five is great. I'd be far more worried if he just followed what his parents did, without question. Do you want to produce a well-rounded person who can think for himself, or a carbon copy of you? I'd say leave him be, and only take him flying if that's what he really, really wants.