Don't laugh. It's a perfectly good question. Think about
it, even using comic book logic he doesn't have what it
takes to fly. No wings like Hawkman. No jets like Iron Man.
Nothing but a flapping cape.

In fact, when he first appeared, Superman couldn't fly. The
most he could do was "leap tall buildings in a single
bound." Being from the planet Krypton, where the gravity is
stronger than on Earth, Superman had to develop super-
strength just to walk around. So when he came to Earth,
leaping tall buildings, running fast and bending steal was
a cinch.

Since, a leaping superhero is probably not the most
exciting thing to read about, by the late 1950s Superman's
writers allowed him to defy the laws of physics by flying.