I use AC3D to create airport runways and taxiways, I think I paid $99 for the software. Rodeo has YouTube tutorials on using AC3D to create a basic airport. ryansumei has YouTube tutorials on how to do airports with crossing runways, and how to do taxiways using AC3D. There’s no audio with ryansumei’s tutorials. I did write out the process using the video.
The link to the tutorial is in the forum under General Discussion-New AC3D Airport Tutorial by ryansumei.
Hope this helps