Having gone away and come back, my advice is to ease the rules and bring bases closer together. The first time I logged on after being out of the game for several years, I was unable to fly a lot of the planes because the ENY kicked in. I know what ENY is, but if I didn't and was logging in for the first time, I'd be puzzled, frustrated and looking to leave since I was being forced to fly F4F-3s and Hurricane Is against La7s and P-51Ds. Quite frankly, I think AH has too many arcane rules intended to force folks to fight how the developers want them to fight. The games that are successful these days have simple, easy-to-understand rules and trust communities to figure out the most enjoyable gameplay.
I've always said AH needs to think more about folks looking to hop in a plane or tank, get into a fight and rinse and repeat. The game setup now requires fairly long flights or drives to get into a fight (particularly when other online games let you engage folks in under a minute), and most newbies are going to skim the surface to be able to engage someone relatively quickly. In AH, they then they get bounced by a vet who is willing to take the time to climb to altitude, so after flying for four or five minutes with no action to speak of, they are back in the tower and wondering why they'd want to do that again. Everyone enjoys a good furball, so encourage them and set it up so people can easily hop in a plane and find a fight. It keeps people hooked and doesn't prevent folks who want to start their flight further out from doing so. Eventually the newbies will learn and appreciate being older and wiser, but the AH learning curve is high and it isn't any fun to spend weeks getting shot down before you can engage. The game needs to be set up with the new user in mind, not the old (and increasingly scarce) pro who objects to quick and exciting fun.