There are lots of other custom assets, like control towers, hangars and parking for planes and cars, as well as a freight terminal.Microsoft Flight Simulator 2020 is, in certain ways, the most technically impressive game we've ever seen.

There are A380s, 737s and some 747s there, which will bring some real life to your airport. Go get some custom planes from the Workshop. Pick ones that confirm they work in their descriptions. There are a few custom ones on the Steam Workshop, but be aware that the “Modular Airport” style assets are cosmetic only. The other thing you need is a functional, yet runwayless airport terminal. This might come in handy for your normal traffic woes as well.

Just to be on the safe side, grab one of the mods that show directional arrows for one way roads from the Steam Workshop. If you get one connector going in the wrong direction, your airport will be a very pretty ghost town. Be very careful with these, because all of these roads are one way only. You will need several mods, chiefly the Airport Roads mod, which allows you to draw your own (much longer) runways and taxiways. So there are a few prerequisites for a custom built airport, and it does require a lot of patience to build. The Steam Workshop is here to the rescue! Again. Short runways, single terminal and short on realism, they were probably the most disappointing features of an otherwise overwhelmingly good game. Look, all I can say is that the vanilla airports in Cities: Skylines are boring. Requires patience and a lot of experimentation

Cities skylines functional airport