Could you make 3D clouds by making a invisible mesh and have it emit particles that are colored the same as the planets atmosphere. Doing it with the spaceship3.dll. It would take a long time to place all the "ships" by hand, so someone could make a program to create the coordinates of each ship. If it were possible to do this fast and effective (To create Movement you could you add a car like movement and drive the vehicle and use the UCGO's autopilot to save movement) it could add more realism to gas giants and moons like Titan or for a dust storm on Mars. Another program could be used to create coordinates for the emitters depending on how thick the cloud layers are.(For the may depths of Gas Giants) Maybe even different particle emitters for a blend thing.