Trees and buildings are static environment and can be mapped. I don't see how bird traffic can compete with road traffic, this comparison don't hold much to me.

Trees and buildings are static environment and can be mapped. I don't see how bird traffic can compete with road traffic, this comparison don't hold much to me. The third dimension is only an issue at takeoff and at landing which are by far the greatest show stoppers here. With maybe economic feasibility. Cars also have road navigation to handle with ugly stuff such as dynamic roadblocks and obsolete maps, all of which don't really apply to flying. Maybe in a mid/long-term future we'll see regulations for drones but it is very close to free for all as it stands right now