Airports

how do international airports work and why cant i build more

Airports are auto built with Air Transport Corps. They have no other purpose that I know of.

Airports are used for relief aid the more you have the more relief you can send

i hope the GM would tell us what the point of Airport Corps are?

also, airplanes, and cargo planes, have always been looser corps? with very little demand, again, GM, can you explain this?

Would be nice or at least common sense,if airports
played a role in selling your corp production,
like in the CM where you have solid trade contracts so one would need cargo planes
to reach other nations the same as rl,or cargo naval transports "sigh".

I have to say that I have never understood the reason/purpose of cargo planes.

cargo planes are used, with airports, to transport relief material. its been years sense i did any of that, so i guess, that's what they used to be used for.

They are still used for relief. airports give 120 flights per day.