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Old 20th Mar 2017, 22:51   #9 (permalink)
stator vane
 
Join Date: Dec 2000
Location: very close to STN!!
Posts: 519
I've seen them before

More than once, in flight, but as to the cause, I cannot add further than some guesses: possible relative variations of humidity, temperature layers, direction of the aircraft, its resultant contrail in relation to dominant crosswind, or perhaps in an area of rather low winds, between changing vectors of wind direction.

Last edited by stator vane; 20th Mar 2017 at 22:51. Reason: addition
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