Are there any flight simulator Wolfenstein 3D mods?
The closest I've seen is a WIP mod based on the Star Wars franchise. It was a "Luke Versus The Tie Fighters" stage, and it played basically like Battlezone in outer space.
If there aren't, it should be easy to create one right?
Not really. Everything in the Wolf3d engine is one vertical plane. You're better off trying to do a hack of the Descent source code.