> Autopilots have contributed to a significant number of crashes and that’s with a very safety conscious industry.
"Contributed to", in the sense that the pilots decided to just blindly trust the autopilot and let it make a developing situation worse rather than, oh I don't know, maybe FLYING THE DAMN PLANE.
> buggy autopilots can surprisingly quickly get into a situation at cruising altitude which isn’t recoverable before hitting the ground
If you allow the autopilot to fly the plane into the ground, yes. If you're paying attention you ought to be able to recover just about anything, if most of the plane is still working. The vast majority of incidents where aircraft have departed controlled flight and crashed are because the pilots lost sight of the important thing - FLYING THE DAMN PLANE.
> But my point was lack of aerodynamic stability on its own isn’t enough that giving up is ok.
It's got nothing to do with aerodynamic stability. If you adjust the steering and suspension in a car correctly, it'll drive in a perfectly straight line with no user input for a surprisingly long way. With modern electronic power steering and throttle-by-wire systems it's actually surprisingly easy to turn an off-the-shelf car (even something cheap, secondhand, and quite old like a 2010s Vauxhall Corsa) into a simple line-following robot like we used to build at uni in the 80s and 90s in robotics class. Sure, you need a disused aerodrome to play with it, but it'll work.
There is the far greater problem that self-driving cars have to cope with a far more rapidly changing environment than an aircraft. A self-flying plane would be far easier to get right than a self-driving car.
A human driver can't just react, painfully slowly, in the way that current "self-driving" cars do, they have to anticipate and be "reacting" before the problem even begins to start. You do it yourself, even if you don't realise it. You hang back from that car because you know they're going to - there, right across two lanes, not so much as a glance in their mirror, what did I tell you? - they're going to do something boneheaded. That car's just pulled in, the passenger in the back is about to open their door right into your - nicely done, you moved out to the line and missed them by 50cm at least.
Self-driving cars can't do that, and probably never will. Self-flying aircraft won't need to do that.
And an autopilot is a surprisingly simple device that responds in simple and predictable ways to sensor inputs.