I thought, somewhere here in the forum someone presented harbors and airports being built outside cities.
Does anybody know, where I can find it?
The forum search didn't give the right link.

Noone knows?

No, not yet.

Chineese American said he made a coastal "port" that serves as a trade connection, its in his MoreTradeRoutes mod. I think it still needed work on the graphics but is providing the trade route effect, I havent played it myself.

Port is an improvement that be built inside and outside your borders, but only on coastal tiles. It connects your ocean-based trade with your land-based trade (don't forget to build a road on top of the port). Also, provides +1 commerce if worked on, and +1 more if you know Astronomy. Can be built on desert tiles, too. (by default, nothing can be built on deserts.) I still need to work on placing the graphics by the water.

I'm working on Runway improvement that works like Airport building. You will be able to airlift to and from a plot with Runway. and of course connecting trade networks, bonus yields, etc.

Ah, OK, thank you

While we are looking at coding could you investigate whether it is possible to code in a military airfield which allows the basing of aircraft outside of cities. It would be good and more realistic to have this sort of idea happen.

Perhaps TheLopez's "Improvements Outside Borders" mods could help?

http://forums.civfanatics.com/showthread.php?p=4206878

I think the more difficult thing would be coding the improvement to begin with.

It would be nice to have the old Civ2-style Airbase back... but I think the airbase would have to give special bonuses you couldn't get from keeping planes in cities because otherwise there's not a whole lot of incentive to build them.

unless you pull a Guam or Iwo and build an airstrip on a 1-square island within reach of your enemy.