If using real world weather a cirrus layer may not be present via the default weather dialog. X-Plane approximates a nice number of possible situations. Set your weather without noaa or default real weather: 30, 000 cirrus 14, 000 cumulus sct 5, 000 few cumulus Set your visibility CAVOK Is this what you are looking for? If so real world weather may or may not have this effect.....all depends on the weather....