I do not have any AI packages. I do not have ground shadows turned on. I have no FS9 aircraft or AI models installed.
That's the problem. If you use default AI traffic, those airplanes are missing the airline codes, and all our sceneries rely on airline codes being present, and they always are in AI Traffic pack dedicated products, which most of users have installed anyway. Besides, the default AI are very heavy on fps, because they are the same models you can fly, so they are not optimized to be AIs.
You probably HAVE some AI but, they are likely parked in remote areas, not on the main terminals, because we flag all our parkings in the airport to be of the generic GA type, in order to get rid of the default FSX ground vehicles which would otherwise conflict with our own vehicles and other ground objects. Several developers use the same method, so you'll have similar issues at other airports too, if you use default AIs
But if the AI has an airline code, it takes precedence over the generic type assignment, that's why it's better to use a proper AI package made for FSX (such as Flight1's Ultimate Traffic 2), that will result in a vastly better airport, with real airlines parked at their own gates, and probably better performances, because those models have been optimized for AI usage.