Technology wise, aircraft are already 90+% automated - autopilot does basically the whole cruise phase, pilots are there to do the communication with ATC, manage the autopilot, and be hands on for taxi, takeoff and landing.
From a legal/policy perspective, the aviation industry is held to a much higher standard of reliability and safety than the automotive industry - the AI driven YOLO that companies like Waymo get away with. It's not just that autopilot systems have to always work, it's that they have to always behave in a predictable way.
I think truck driving is probably the next thing. There's laws (at least in the US) about how long a driver can run without rest, long haul routes are generally not very crowded with traffic nor complicated. If you can get twice as many hours out of a robot than a human, you can recoup the investment pretty quickly. I could see a hub-and-spoke model where robots handle the long spots with humans taking the busier spokes.
I'm surprised it's not already in place for rail freight. Pre-defined, well known routes, automatic right-of-way. You'd need some exception detection - spot things on the line or if any part of the train is behaving abnormally, but like cars you can "fail safe" - do an emergency stop if the computer or a remote operator decides that something has gone sufficiently wrong which you can't do in a plane
It already is for some specific rail freight, iron ore haulage in Western Australia being one example. Rio Tinto has been running them in WA since 2019.
The Sydney Metro is also driverless, albeit a passenger only line rather than freight.
Im going to guess its a proportional cost issue. Drivers take up a much larger percentage of the cost of shipping a ton of cargo by truck that the cost a human engineer on a train.
No, there really aren't yet. Driverless taxis and delivery vehicles are all "monitored" remotely by people who effectively drive them when they get into situations the automation can't handle. Individual self-driving cars all come with a lot of warnings (which many drivers ignore) that they require an active and aware driver for similar reasons.
And Tesla, who have been lying about their self-driving capabilities from day one, continue to run people down and smash into other vehicles on a regular basis.
The systems are good enough to handle 99% of the driving situations they encounter. That remaining 1% is still a long way from being solved. And "pretty good" is not acceptable when failures kill people.
They not working in all cases is a qualifier you are adding yourself though. There are definitely existing self-driving cars. There are no self-driving cars that can handle all situations, but being perfect or finished is not a prerequisite for something existing.
Airplanes, though I suspect they will never be truly without someone to assist in case of emergency.
Cars have to contend with a number of random obstacles and unique challenges. Planes have defined runways and taxiways and, via autopilot and GPS, their flight paths are relatively easily defined and controlled.
The sky over one city is pretty much like any other. Main Street not so much.
Airplanes will never be pilotless, there will always be a human in the loop for redundancy. A failure in a self driving car could kill a few people at most, a failure in a pilotless plane could kill thousands.
Driver less cars, because cars in the US have less safety regulation and laws applying to them, so the US is likely to continue trying to make them a working technology. Planes already have alot of automation, but law requires a human pilot with alot of training.
Come to think of it we already had driverless vehicles, they were called horses. A trained horse could probably get you back home safely even if you hapoen pass out on it. But it still wasn't common practice to take a nap on a horse back.
My grandma always told of a legendary man in my hometown, who would always take his horse to the local bar in the 1950s. When he got too drunk and fell asleep, the other patrons would carry him outside and sling him sideways over the horse, which would then trot off in to the night, supposedly delivering him safely at home.
I know that's not very scientific evidence, but I always took it to be true. Maybe someone can concur.