electric would be the way it goes and you could argue that flying drones flying at a constant speed could be more economical than a self-driving car limited by the current road infrastructure.
At least with current technology, electric makes the energy consumption problem worse rather than better, on account of the poor energy density compared to combustible fuel. The difference is manageable with cars, but with aircraft, where you have to take all that extra weight and pull it up in addition to moving it around, things get to be pretty stark.