Well don't let something like flat feet stop you! If you're really interested in joining the military there're lots of vocations that don't require pure physical abilities.
Administrative work is just as important as any work done by the guys with their boots on the ground (or in your case, in the air ). I'm a signaller by training but from where I come from, signallers tend to do quite a bit of admin work during non-operational periods so I've been able to relate to the clerks, I/Cs, admin NCOs, etc in the various HQs and over my two years, I've come to hold a deep respect for some of the really hardworking ones. (y)