Currently I think the Air Range promotion is too vital of an upgrade for aircraft. Aircraft Range is too short normally, there are lots of times when I'm out of range in common combat scenarios, and the +2 range from the upgrade is just huge. The only time I have forgone the range upgrade is when using planes from carriers, and then I inevitably regret it once I take the sea and my planes move to land. I recommend the following: 1) Increase the range of bombers by 1. 2) Decrease the range upgrade benefit to 1 (down from 2).