A plane autopilot is supposed to be capable of flying the plane unattended and handing over control in an orderly, controlled fashion before critical problems arise [1]. A ships autopilot is expected to do the same. The same should be expected from a car autopilot. The fact that the environment is much much simpler for planes and ships doesn't change the fundamental expectation. As long as car autopilots are not capable of fulfilling the expectation that they can autonomously and safely control a car in a given real-worlds environment with other participant they should not be marketed as autopilots. They're driving assist programs.

[1] there are examples where this did not happen, but they're considered a failure.

As far as I know there isn't any autopilot that can fly a plane unattended unless you are flying on instruments. Collisions are avoided by relying on the air traffic control system knowing where all the planes are scheduled to be. (Plus plenty of backup warning systems.)

You can still use an autopilot when flying visually but then it's up to you to watch for traffic. This is using it like cruise control.

> Collisions are avoided by relying on the air traffic control system knowing where all the planes are scheduled to be. (Plus plenty of backup warning systems.)

Yes, perfectly fine. If Teslas autopilot can rely on external traffic control to provide that information, call it autopilot. As long as it can't don't.

> As far as I know there isn't any autopilot that can fly a plane unattended

CMU is working on this (seriously).

A plane's auto-pilot maintains bearing, altitude, and speed—seems pretty similar to "lane assist" / tesla-autopilot to me.

Some can land, in optimal conditions, but can't taxi.

Landings are also mostly automated just through a different system(s) https://en.wikipedia.org/wiki/Instrument_landing_system https://en.wikipedia.org/wiki/Autoland

Have you tried Tesla's autopilot? It's not far off from your description.

I haven't. As I understand it, it basically doesn't work at all in city traffic? Like going across Manhattan on 59th street?

That seems roughly equivalent to taxiing in a plane, something which isn't handled by a plane's autopilot. After using it, it feels very intuitive to understand what it can and can't handle, and it does degrade very gracefully (beeps at you and says 'take steering wheel to maintain speed' if it starts to get confused.) It works very much how I would have expected knowing nothing more than the name.

I can't detect red lights unless the car in front of you stopped for one. So not really.

But a technically very similar set of features results in a vastly different user experience. A driver with a Tesla autopilot has a way smaller margin of error and needs to react a lot quicker once the autopilot encounters a situation it can't handle. Flying planes generally have way larger error margins, and a lot of effort goes into making sure they are nicely separated from traffic and obstacles (and when they come close, it's known early and the pilots can get ready to take over). Until we have highways with similar traffic control cars can't match that without a lot more intelligence.

For one thing a plane's autopilot doesn't automatically avoid obstacles.

There are other systems on the plane (TCAS, ATC communications) that provide information about conflicting traffic. Does Tesla provide those? Will there be enough time to react if it did?

There are far fewer obstacles in the air than on the ground.

If you put a plane on autopilot and then go read a book for some hours, most likely nothing bad is going to happen (particularly on IFR, but even on VFR, realistically).

Tesla's autopilot is more advanced than aircraft autopilots, I'd say, yet more dangerous (for now) because of all these darned cars and trucks and pedestrians.

In that sense, "Autopilot" was an unfortunate and overly ambitious name.