@vic.foras use blimps and helicopters and they behave as you would expect. (lifting and descending instead of "landing" the way planes do.) Spaceport would be cool though. But you can mimic one by placing a bunch of helicopter stops and blimp stops near each other, then detailing the surrounding area to feel like one big port.

I wish Cities had a Spaceport DLC, to use these wonders. Unfortunately, the behavior of the airships is a bit silly, so it's not cool. But thanks for the addition, there will definitely be someone who will use these assetts in wonderful ways.