Natural monopolies are physical monopolies. There's literally only so much room on the Earth's surface. So to the extent that anything is being stifled here, it's because two objects can't occupy the same space at once, not because governments have anything to do with it.

And the challenges airplanes face are very physical as well. It's not really the government's fault if no one proves ever capable of making flying cars safe enough for the airspace above cities to be full of them. At some point it's just an intractable engineering challenge and the limits of human ability.

Personally, I'm doubtful that flying cars will ever be a reality in our lifetime, but the only possible way I envision them ever working is if they're 100% autonomous and owned and operated as a fleet.