I want to suggest to some people, to read the first post of this thread. People are saying that he can use Super Nova and etc, but... He can't. Just read the first post, please.
And why you guys, think that Sephiroth can fly? Before Nibelheim, he can't fly. Only after he come back of his "dead" in the game, he can fly, and this is because he is using Jenova's powers, like he did in the movie too. Before Nibelheim, i remember a moment that he, Cloud and the others, fall of a bridge. And in the Mako Reactor, Sephiroth fall in the Lifestream. These are two moments, that prove that he cannot fly.