Wheeled vehicles have lots of opportunities for braking, but airplanes and boats not so much, so even if you could do regenerative braking (which you probably can't) it'd not be enough to be worth doing. It's a loss compared to wheeled EVs of 30%-50%.

And then airplanes typically need to be lighter when landing than when taking off, and jet fuel has the nice properties that a) as you use it up what you've left weighs less, b) you can toss enough jet fuel to get to landing weight if need be. Batteries have neither of those properties, which means that electric airplanes would have to be built much sturdier (i.e., heavier, therefore more expensive and less efficient) to handle heavy landings, or would have to carry less cargo / fewer passengers per unit of stored energy (i.e., less efficient).

I'm afraid that no matter how good wheeled EVs get, it's going to require a whole new kind of battery before you can ever get to practical. large electric airplanes.

Electric will start smaller and build up to big just like everything else. The single and twin engine world is pretty dominated by structure so the gains are easy to see there. As new capabilities and designs are prooven out things will grow or, and this is what I really hope for, we will find that we don't need the massive aircraft to be profitable anymore and we will just get more smaller electric aircraft providing the service in a more point to point nature. One of the biggest efficiency gains we could have is not forcing people into a hub and spoke mega airport model, something that isn't practical with the current massive aircraft tech.

That would be terrifying.