We've got boats, we've got trains, we've got... rockets? But no planes.

Now, we've got enough logistics options as it is, and the maps are small enough, that I don't think it makes sense to try and use aircraft as an island logistics solution. We've also already got mechanisms for instant trade, loans, adopting and evicting residents, and attracting refugees with a Beacon.

But an Airport could still provide income from tourism! What income, you ask, in a world where money is meaningless? Unity, of course!

And perhaps we could even manufacture aircraft for use as trade goods. Or as faster "cargo aircraft" with lower capacity than similar-rank cargo ships, higher fuel burn... and the ability to carry products marked as "highly sensitive"- that might realistically spoil over the duration of an ocean passage, that is.

If paired with my thoughts on an expanded/unlimited World Map over in my Drydock suggestion, then passenger aircraft could be used to bring tourism-based Unity... but combat aircraft (possibly paired with aircraft carriers) could be used to scan World Map locations- a la Radar- and possibly even bomb pirates into oblivion without ever sailing a ship anywhere near them. These aircraft couldn't reap the rewards of an exploration, except perhaps to a settlement (and perhaps not every other settlement should have an airport). They might, however, be able to carry significant amounts of cargo over very long distances relatively quickly- say, Donations, for example, to improve settlement reputation.

Something that might make a fun difficulty option (and likely very complex to implement) might be to acknowledge the fact that, in the real world, landing doesn't always go as planned- particularly in poor weather. That basically always means a "go-around", where they abort the landing and make another attempt. That's different from basically every game I know that simulates aircraft in that it necessitates open flight path at both ends of the runway, and possibly designated approach/missed-approach routes. Those other games always have a "planes always land perfectly" simulation quality, and I personally find that immersion-breaking. Why not make them sometimes have to swoop around for another attempt? It'd be fun to have regional and terrain design constraints based around aircraft clearance, an extra challenge for the larger/taller buildings like bridges and rockets. And terraforming projects...