Subways are little more than dry sewers, which is a little disappointing. I guess you could have airplanes act like cars, just on a different z-level and it has the ability to freely travel (i.e. teleport, deconstruct, reconstruct) So you’ll press the vehicle menu, go up or down a certain amount of levels, etc.
If that’s not probable (Which now thinking about it won’t have much utility) I think it’ll act like pressing M and viewing the map, allowing you to fast travel, drop bombs, scout, etc. would be much better than just pressing the drive key and staring at blue tiles for 15 minutes while you travel in one direction.
(Not enough fuel to reach destination, land as close as you can? Y/N)
“Drop bombs where?” (Shows blinking letter)
Adding the potential to drop atom bombs from airplanes would be the cherry on top.