Would it not be fun to just strap on wings and fly? There are problems with Earth's thin atmosphere, but why not just make it denser?
Releasing gas from undergroundEdit
There is lots of fossil nitrates and ammonia underground, with nitrogen stored away during geological time. Why not dig it up and denitrify it? That would release lots of nitrogen, making the air denser. There may also be subterranean deposits of noble gases to let out.
Bring it from spaceEdit
There is gas elsewhere to bring to Earth. Titan (moon of Saturn) has a lot of nitrogen in its atmosphere, and Triton (moon of Neptune) is rich in frozen nitrogen. And if you have a good CO2 scrubber, you may bring it from Venus as well.
People under extreme stress are known to have lifted cars and helicopters. That force would be enough to fly with strap-on wings. The drawback is that extreme stress would make it less fun to fly. So making the atmosphere denser is a better idea.