If the engine cuts out in a helicopter the pilot can use the energy still of the rotating blades to land. This is called an autorotation landing. But this is no guarantee of a safe landing.

You are assuming that the gas gauge is working properly. If the engine in your flying car fails for any reason you are then dropping like a stone.

Let me guess that you will come back and say the vehicle could have a parachute. This is true. It would be an expensive piece of equipment. So you would be hoping that one of the service technicians hasn't stolen it. Lookup stolen air bags if you think this can't be true.

The other big problem is if you run out of gas then you fall out of the sky.

No, if nothing else kills you the heat death of the universe will.