I don't get your argument. Humans can safely pilot airplanes at 600 mph, but clearly cannot do this safely on the ground. The difference is density. Cars routin

I don't get your argument. Humans can safely pilot airplanes at 600 mph, but clearly cannot do this safely on the ground. The difference is density. Cars routinely travel only a meter apart on highways, but because there's a lot more space in the air, planes maintain minimum separation of hundreds of meters. Ships, also driven by professionals, collide more frequently than airplanes for the same reason. Another important reason to go 3D is that you can go much faster with less fuel at high altitude.