Re: Municipal Airport
Hiya @alwe15! So sorry it took some time for me to get back to you on this. The holidays are very hectic for me, so not a lot of gameplay time lately 🙂
I seem to remember also having an issue when I was first figuring out the airport. I think this is probably just an issue of trying to place things in the wrong spot. I made a test area and was able to fully upgrade the municipal airport. Couple things - you can build on any type of road, so no worries there. The sign goes on the building, not the on the road, so look for the blue dots there. The cargo and passenger terminals will only attach to the main building, and only on the right (if you're looking at the front). Try adding the building extensions before you add any more runways. Maybe you blocked the spots with a runway?
Here's a pic of one fully upgraded, on a low density road:
Hope that helps! Happy Building!