I was under the impression that since the majority of the ships we see float anyway like those hoverbikes we see the Al Bhed use, then other airships that transport the crew later and can be seen around the blitzball tournament were run on machinery. I mean... you say white magic but... i recall you get to go on an airship (or was it a boat? You got on a lot of different forms of transport in-game) where you go into the engine room and its just a chocobo running on the equivalent of a hamster wheel keeping the thing going.