I had always used cheat devices when I played VII, but I am playing it real now (yeah, I know I suck).
I am on disc two, and I have the Highwind, I can now fly to the cave where I get the mythril to trade for Great Gospel. But I can't see any obvious way I could have gotten to this cave before without the Highwind, but there has to be a way because it's Aeris' limit, and you only get the Highwind on disc two.
I never bothered with this before as I had all Limits through cheating.