Simple solution: don't let them control the vehicle. All they'd have to do is input a destination, and an autopilot could do the rest. Make it so that flying vehicles could communicate wirelessly and avoid collisions with each other, and safety should be pretty easy to achieve. I'd feel a lot safer being driven around by a robot with sub-millisecond response times than I would by some bum who keeps staring into space and talking on the phone at the wheel.