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.