I am latest in the manga chapter. So I know the history behind Koro-sensei. But I wonder how can he fly? I mean, I know he is super fast. But being fast doesn't mean you can fly. And he don't have any psychic or esper powers to levitate or fly.
He may be fast to run in the air or something like that. But when he is flying he is not upright, he is laying down like super man.
He may also use his tentacles as propulsion, but as seen whenever he is flying it seems his tentacles are just there.