Black lines in the sky.

[CoastGuardJon]

I've noticed this before on the odd occasion - watching and studying the vapour trails of high flying aircraft, ahead of the aircraft is darker line, has anyone else noted this phenomenon?   It is as though the a/c's course has been drawn for it.   I've wondered if it could be the soot in a previous a/c's exhaust (as in multiple USAF a/c following the same course), but this would get blown around and dispersed.   I've yet to successfully photograph this odd effect - has anyone any rational explanation for this?
CGJon

[Team Spirit]

Hello CGJon,

Yes, seen this too...It's probably the Sun creating a shadow of it's vapour trail. Need to take a picture of the aircraft and Sun position to work this out I guess.

Cheers Dave, East Devon.

[Runway 31]

I have also seen this before and would also suggest its a shadow the vapour trail from the aircraft.

Alan

[Hawkeye]

Also seen this dark line in front of aircraft many times but can only recollect it occurring on the ones either travelling roughly E to W or W to E.

I too feel it must be a shadow of the contrail created by the sun but it seems strange that, in my experience, it has only appeared as an 'extension' in front of the trail, (when the sun must have been directly behind the 'plane), and never as, for instance, a line parallel to it when the sun is abeam the plane.

Regards
Syd

[CoastGuardJon]

Well, thanks Dave, Alan and Syd, I must admit I hadn't even considered it could be a shadow, the one I saw yesterday was flying nnw probably 7 or 8 miles west of me over Mounts Bay, and I think it was about 1530 so the sun would probably have been behind the a/c relative to my position.   I'll try to get some pics, and will note sun position relative to me and the a/c.

[Aerotower]

 Sun creating a shadow of it's vapour trail.