is he compatible with any flying tm's?
I suppose I am rather late with responding to this, but oh well.
In the first generation, Gyarados actually worked as a mixed attacker. His special attack stat in that generation was equal to Mew's. In second generation games, he was used almost the same way, just with slightly different attacks. Still, no flying moves were placed on him.
In third generation games, people saw it fitting to give him Hidden Power (flying type, of course). This was almost useless in-game, though, since one could almost never get the right type. Even then, the power cap for it was 105 on Gyarados, and that was just as difficult to accomplish (IVs).
In fourth generation, though, I guess they finally got around to wanting a flying move on Gyarados. On Platinum version, both Gyarados and Magikarp can learn the move Bounce via move tutor, a physical flying attack with both power and accuracy of 85 (of course, it has a power of 127.5 when used by Gyrados, though).
/ramblings