On planes pilots generally have time to take over if the autopilot fails. Falling from ten thousand feet takes a few minutes.

On cars, if autopilot fails, the driver might have a fraction of a second to recognize the failure, take over from the AI, and initiate corrective action. Generally, there isn't sufficient time for any of these steps, let alone the first one.

Pilots have significantly more training than drivers. Safety is drilled into them from the beginning and how to respond in emergency situations is continuously reinforced with recurrent simulator training and testing. There are also far fewer interactions between an airplane and physical elements of the world than with cars. Weather visibility is much less of a problem except on takeoff and landing. Finally, on commercial flights there are at least two pilots operating the aircraft at one time to balance the workload.