Flight is just membrane-assisted jumping.
It is exactly the sort of process which evolution is really good at refining. I don't find it all surprising that it has evolved in bats as well as in birds and insects. Most of the other marvels of evolution are also processes which can gradually be refined. There is a continuum from fins to the legs of cheetahs and from simple excitable cells to the vast neural nets of our brains. Vision is just a refinement of chemical photo- sensitivity.