During take-off last week on my Sunday Morning Flight, I noticed a fascinating thin vapour trail above the wing, coming from the jet engine of that Boeing 767-200ER:
Vapour Trail from Jet Engine
It was a very sharp vapour trail, and very interesting to watch. At the very least, it showed the aerodynamics of the wing. And the sun made the outer area of the trail kind of glowing:
Vapour Trail above Wing (click to enlarge)
The phenomena disappeared after about 30 seconds: so not to worry about loosing fuel ;-). But what was it? After asking around, finally a got the answer: It is generated by the vortex generators on the engine. If the atmospheric humidity and dew point are right, such trails can be observed. Explanation and more about this cool phenomena is in “Thin Vapour Trails Above Wing“. Aerodynamics can be sooooo cool.
Happy Trailing 🙂
MCU on Eclipse 
That looks so cool!
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Adiabatic decompression of that particular part of the airstream over the wing… in relatively high humidity, causes “fog” to form. I’ve seen this thin stream myself. Sometimes the entire surface of the upper part of the wing is covered by this local “cloud.” Have NOT seen that myself, but have seen pictures (http://en.wikipedia.org/wiki/Condensation#mediaviewer/File:Cloud_over_A340_wing.JPG)
Personally, suspect that some local effect caused by the engine nacelle makes the air pressure slightly lower in that thin area, resulting in the tiny stream of fog. Is is VERY neat to see.
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Great pic showing the laminar airflow over the wing, and both the reflection and the shadow of the vapour trail.
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