Guys,I was just wondering if missing vapor trails would be caused by AS? Usually the trails should start showing up from FL300, to my surprise the trails are missing not only at the aircraft I'm flying but also the AI aircraft. Just as an observation, using default weather does not take away this effect. I'm using 7th beta version of 1.91c.Any input on this would be greatly appreciated.

I assume you are using FS9, you did not say. If not, you are correct, all trails start at FL300.If you are using FS9, trails start based on temperature. Your aircraft and AI will produce trails at altitudes based on season and latitude, which is much more realistic. I think the default setting is -30C, and it can be changed by placing the variable:max_contrail_temperature =into the GeneralEngineData section of the aircraft.cfg file.Bruce