Hello!
I have a simple suggestion for gameplay mechanics.
-A new building could be built, it would be called an airbase/airport, and with it you could deploy, trade aircrafts, and fighter aircrafts. It would work just like the boat mechanics, but in the air (trades crafts go between airports and fighters intercept them, etc), and if possible another plane, like a bomber for example (it would be up to you to decide what it does I have no idea lol)
A reply would really appreciated