There is so much hype on driverless cars, but I would imagine that is technologically simpler to build and deploy a pilotless plane. Comparing to a car on a road, the traffic and encounters with other vehicles are much more predictable (and avoided), terrain is much more known and permanent, and there is much more external monitoring (from the ground).

It may piloted remotely or even self-piloted by a computer.

Is there anything I am not aware of? Being it around technical challenges I did not antecipate or serious investments already happening that I don't know about?