Manually-driven flying cars are a terrible idea even if they were physically practical, which they're not. But I could see flying cars driven in fully automatic mode by a sufficiently advanced autopilot being OK from a safety perspective.

On the other hand, if everyone is using sufficiently advanced autopilots, ordinary non-flying cars become much less of an annoyance. The great flying-car fantasy is a fantasy of soaring above a traffic jam; networked flow control for autopiloted cars could eliminate a lot of jams in the first place.