Ive downloaded a couple of models which are a number of planes in formation, namely the Red Arrows and the Thunderbirds.
They cant fly very high before they dissapear into the clouds, so could FMS include an option for setting the height of the cloud base, possibly even the density so you could set it at ground level as fog! (Is if its not already hard enough to tell which way a heli is when its far off)
Deffiant "To the choppas!"