It's something related to the airport, but I don't know what. Maybe Virtuali can chime in here.
No, it's not. More precisely, it is related to the airport, but it's caused by your AI.
The AFCAD for KLAS, of course, comes with all proper airline code assignment, to control traffic on the proper stands, by airline. But if your AI planes don't have airline codes in their aircraft.cfg, they might not appear, or might appear in the wrong places.
Another possible reason is if you have some AI models or an AI set which was originally made for FS9 and then converted. This are known to be invisible, if the scenery use some special custom runway texture so, they work on some airports, but not on others.
It would have been helpful if you said *which* AI you use, especially if you installed a combination of things, like commercial+freeware addition, or made your own set by combining different freeware products.