> Autonomous vehicles should not communicate with each other. Waymo's cars don't. Most of the schemes for "car to car communication" are motivated by marketing or surveillance, not driving. Aircraft systems don't communicate with the ground much, and when they do, the uploaded data is very simple. (It's common in commercial aircraft to hardware disable maintenance functions unless the "weight on wheels" switch is on, indicating the plane is on the ground and parked.)

You seem to be out of touch what happens today. Car2Car or Car2Infrastructure is about as aircraft to aircraft communication is used in TCAS. It is about what car (object) is at which position, so that collision may be detected as early as possible to prevent them.

Also next generation cars will have their maintenance modes locked down as far as possible. OBDII will be closed down as far as possible. All those dongles, which are hip right now, will be rendered useless. But of course the tuning scene has still a lot of incentives like in the past to thwart all this and to reverse engineer. It will be a cat-and-rat game like it always was.