Civilian Airports

Is there any documentation on civilian Airports? I have looked sometimes, but have never been able to find anything about them. Also, I can't find these [non-military] Airports on the products page, so how would you get more of these, or remove them? I have two of these civilian Airports, and I assume they either have an effect on migration, or they are merely there just for show. Perhaps there's something there, and I just hadn't noticed. If there is some documentation about civilian Airports, can somebody point me to what section to find so I can read about what purpose or effects they have? Until I can find some documentation I have the impression that they although there may have at some time been a plan for these Airports, they have not been fully implemented, and that the presence of civilian airports does not yet do anything. I have just been, over time, becoming increasingly curious to know if anybody knows anything about civilian Airports.

They're Air Transport corporation symbols. Instead of a factory it's an airport since well.. its Air Transport. Any country with air transport corporations will have civilian airports. They serve nothing more than a target or symbol like a factory.

Aaaahhhhhhhhhh that explains alot, thanks.

Also to add Air Transport corporations can be pretty profitable too.

Yes, I've noticed that, although never had the realization that they are the airports.

Another thing to add which may be important. If you're ever building a country up fast and you're building 3 corporations per month your country will only build one air transport corporation per month. So if you say have 1 air transport corporation and 2 construction corporations ordered the next month only the air transport corp will be built the following month even if you have the 3 corps booster. If you have 2 construction corps first and an air transport as the third ordered it'll only build the two construction corps. Which means you'll be wasting the booster. This is important to know.