cursive dawn
This can also be counting air trade, to access air build a airport and then you can build bombers that sort of work like nukes that will fly around stationary circle around a certain area and drop multiple bombs, or maybe a air type that redirects and hijacks planes into coming into your airport for trade;
You could also add if planes fly to different nations their population increases whoever got the plane, and whoever sent the plane loses population but then there would be like three types of planes so that would be complex
rare loom