[mikepurvis]

Isn't airplane autopilot considered to be significantly easier than automobile autopilot? Fundamentally, it's PID to track a bearing and elevation, and the worst kind of emergency it's likely to encounter is rough weather or some kind of mechanical problem with the plane itself, neither of which need to be handled with sub-second response time the way many road emergencies do.

I get what you're saying about the physical/strategic split, but my perception is that automobile autopilots are simply not good enough to be trusted with the "physical" stuff in a hands-off way like an airplane's can. And that's mostly because driving a car in a straight line down a highway is way harder than flying a plane in a straight line in an empty sky.