RTF is a global modification that replaces all towns in the game.

No, I just encountered some difficulties in implementing the air dragons.

Could you provide more details? What are you working on? What changes are you making? As far as I understand, the most suitable donors would be crystal dragons; you shouldn't need to significantly change the number of legs, the shape of the wings, or the head. You need to add an effect similar to the one on Ilat's artwork and remove the ridges along the spine (you can simply make the texture transparent there).
P.S. For reference, I'm attaching Ilat's artwork.