No such thing exists in the air. The air is mostly empty, there are no stationary objects next to the route. If there is a building, aircraft can fly as far as 500 meters away from it - try finding a driveable road with no obstacles at that distance. There is no people or large animals. There is not even curb to hit.
Importantly, I bet there are no legacy vehicles in the approved routes - and I am sure they will have some sort of V2V tech to ensure that all objects in the air will transmit their position and intention.