I play via family sharing, so I can't comment but discuss...

To everyone with problems, the Airport is in the Intersection part of the building menu because you first place the roads taxiways and runways. After that look in the description of the mod, there is a collection with dependencies and a youtube video howto place the terminals and connect the taxiway. The video is a little bit all over the place but it worked for me and people are enjoying their vacations/business trips.