The problem is caused by your very bad video card graphic settings and doesn't have anything to do with the airport, since you can clearly see a very low quality in the surrounding textures that are not part of the airport.
The problem is more visible if the airport uses custom runway textures, that's why you think it doesn't happen in other sceneries, since many of them use default textures.
To improve the texture quality, do all the following:
- Be sure you set the Max Texture size slider to the highest level. In FSX:Steam this is enough. In FSX SP2, you must use the Addon Manager menu to set the texture resolution to 2k or 4k, because the UI in non-Steam FSX doesn't go higher than 1k, even if the sim supports it internally.
- Be sure you use Anisotropic filtering in the FSX graphic settings.
- Configure settings on you video card to enhance/override application settings for Anisotropic filter, and use 8x or 16x.