This means that for a 100 km trip, a flying electric vehicle (think of a drone big enough to take passengers) would be more efficient than a current internal combustion vehicle (both with one occupant), but less efficient than an electric vehicle. If, however, we limit VTOL (vertical take off and landing) craft to at least three passengers, and compare that to the average occupancy of a car (1.54), the VTOL craft is more efficient than both.

What all this means is that a VTOL craft would be right there in the mix in terms of efficiency, and not horribly less efficient than any ground-based car. VTOL can be more efficient if we limit them to longer trips and more passengers. The authors therefore conclude that they may have a niche role in transportation.

Having a niche role is always tricky. That means you probably can’t just have one flying car as your family car. This is what has limited the market for all-electric vehicles. They have a limited range and long recharge, so having that as your only car can be limiting. But they are great for regular commutes, so for families with more than one car, an electric car can take up one slot. Eventually we will get the range long enough and the recharge time short enough that this will no longer be a barrier to adoption.