Well, that depends on the purpose of the airplane. We already have electric sailplanes which have basically just enough battery power to get the sailplane into

Well, that depends on the purpose of the airplane. We already have electric sailplanes which have basically just enough battery power to get the sailplane into the air, after that you don't need an engine. Plus battery storage has been improving at roughly 10% every year. Right now a flight of around 25 minutes is the point at which fuel makes more sense than batteries but as batter tech improves that number keeps going up. We are at the very early stages of electric flight and while it may never be a viable option for commercial cross country flight there is a good chance that it will take over a lot of the smaller, general aviation aircraft.