@Simbax I don't think I'd be good solution, since flying still would have all it's advantages. Think about Vulcan-1, where you are forced to traverse (small but small) labyrinth because jets don't work there.
Ground robots could just straight up use electric engines, and flying robots could use air as fuel. But then that would mean no flying on planets with no atmosphere. And honestly, I'd be fine with that because flying is OP
But because we can't use air as base for fuel, we'd need to take base for fuel with us. Which is basically pointless, since you could take fuel instead
Still, if you were to change one molecules into other, most sensible would be using local air to do it. Otherwise you'd need to take fuel for nuclear converters, and at this point you'd be better of actually taking raw fuel for engines
I think combustion engines are powered by some renewable power source, but they need some electricity to run it somehow, I don't know, change mollecular structure?