True, but that's where the difference in intended usage is problematic. In the sky, autopilot can't accidentally hit another plane or barrier because it got confused about the road paint or construction signs. The stakes are a lot higher on the ground, even though it technically controls less of the vehicle than autopilot in a plane does (acceleration, braking, and steering compared to elevator, trim, roll, pitch, throttle, vector) since cars don't have to worry about 3 dimensional movement much while airplanes do.