Try unchecking "Fog" in the graphics area (top control bar). This will darken the sky (blue) color.

Is it only the white models being lost, or all models? Or is it that the models are high enough to be beyond the "sim's reach"; I remember something about that from the dim past, i.e., all models will disappear beyond a certain height.

Look back in the landscape folder and find Perry's website. Look for and download his GOUSA day and night sceneries, which are the best I've ever seen for FMS; sorry, I'm not near a way to find a link now.

Best of luck.

Stew