To me Air base just makes no sence in a game like this. Really you can easily fly planes on any flat surface, whereas a naval port is a substantial installation that includes dry docks, fuel depots, etc.
Major naval ports that facilitated and could accommodate military vessels were more specialized, while air bases could be formed ad hoc and improvisation depending on the military situation.
I think they just added them because it fitted into the Land ( factory), Sea ( port), and Air ( airport) motif of game design. The design didn’t seem complete without one new installation for each category. But this was a mistake. It is the same type of thinking that produces 5 IPC for NO’s, or when people design costs and use numbers like 5,10,15 ( nice looking but totally inadequate in terms of game play). It is almost like numbers like 2,3,4,6,7,8,9 don’t exist.
Anyway this air base thing is just another ‘fit’ to the design. But it really adds nothing. If anything it just adds more complexity and not more ‘fun factor’
Also, my naval ports protect ships from naval attacks. This is the key use that they serve as well as construction and repair. But the design neglects to address this substantial concern, and rather invents this concept that ships move faster when they leave the port.
Also, in case many don’t already know this: The entire concept of Major and Minor factories in AAP40 are nearly the same as World War Two: The game ( major builds 10, minor builds 3, costs similar too) The only difference is in the WW2 game, the minor can’t build battleships, bombers, and carriers nor can they be bombed.