Costs: Very High Cost for the "Station" with low cost for the Airroute. (Overall very Expensive and thus only viable to use very late to connect different Train Networks over Oceans or to different Countries.)

Airport Station: No natural growth so you have to transport everyone to the Airport and away from it. Includes

Flight Route: Just a line your planes take from one place to another. Best if invisble if you not in Build mode.

Airplanes: I mean, obv. right?


Reason:
I wish to connect Train Networks i build in different countries and i know others would like too. But building a Train trough the Ocean doesnt really is as fitting.