But you have more time to react on a plane and switch to manual override. It's not like people fly with just a few meters distance to other airplanes. There's also a good distance to the only other thing you can crash into, the ground, as opposed to driving between walls or with a cliff to one side.

Reliably implementing a few control loops and exhaustively testing all possible input/outputs for bugs - difficult but manageable.

Reliably implementing image recognition from multiple cameras and AI that should respond to ever changing weather, inconsistent roads, signs, maps and other human drivers erratic behaviour within milliseconds - Not even in the same league.

Not saying aircrafts are simple but self driving is just orders of magnitude more complex. Otherwise we would have seen them on the roads already.

Aircrafts also have much stricter maintenance schedules, failure investigations and completely different economic, media and moral incentives.

Aircraft autopilots and fly-by-wire systems are vastly more simple than self-driving cars.

Depending on what fails how in a car, you may have less than a second to recover.

Apart from being hit with a high-explosive anti-air missile, I can't think of any failure mode in a plane that has such a narrow recovery window.

737 Looks like cables, air, and hydraulics to me.