Could we power airplanes with ethanol? I've heard that we couldn't realistically grown enough corn/canes to produce ethanol for all cars, but if cars are electric, could we potentially produce enough ethanol for airplanes?

If we can't make enough ethanol for all air travel, I'm still optimistic. It's likely that battery densities will become good enough for us to have electrically powered regional jets within the next decade. Then only long flights would need liquid fuels. As a last option, we could also switch to high-speed trains for continental travel.