I think the energy economics are different for planes and cars, though. There's no equivalent of regenerative braking, or for that matter stop-and-go traffic, for planes.
And adding weight to a car doesn't make it use more energy at high speeds, which is how an old van can get 15 miles per gallon while a fully loaded semi truck gets 10 miles per gallon. Adding weight to a plane does make it use more energy. The effect of adding weight is relevant because batteries weigh almost 500 times as much per joule as fuel does.
Right, but you don't need an electric airplane to do that. With cars, electric is much more efficient for stop-and-go driving because regenerative braking becomes possible.
And adding weight to a car doesn't make it use more energy at high speeds, which is how an old van can get 15 miles per gallon while a fully loaded semi truck gets 10 miles per gallon. Adding weight to a plane does make it use more energy. The effect of adding weight is relevant because batteries weigh almost 500 times as much per joule as fuel does.