Dear Mr. Simpson:

I can assure you, with ALL of my 36+ years in aviation (as a pilot) and my last 24 of those years as a pilot at a major airline, to include being a Captain on the DC9/MD80, the B737 (almost all variations, including the 'NG's) and also retiring from the B757/767 (they share a common Type Rating)...I can verify, with NO reservations that modern High By-Pass TurboFan engines do NOT "smoke"!

Whenever a photo, or video is taken, or made that show a contrail...let me emphasize...a CONTRAIL as looking "dark"? It is merely a factor of the lighting...specifically the ANGLE of the Sunlight that is illuminating the scene. I hope I do not have to steer you towards a college course in photography and cinematography? Because, these standards of lighting angles are well understood by professionals in the business of either making still photos, or motion pictures.

I would encourage you to seek out some qualified photographic experts, before you continue to make claims that can be so easily debunked!

EDIT: Many years ago I was given, as a birthday present, a Minolta SLR camera, with two lenses. I learned a LOT about photography, with that camera...it was an SRT-101...you may look it up online. Sadly, I no longer own it, but I still treasure what I learned from it.

EDIT #2: When contrails "appear" to be "dark"...it is ALWAYS a factor of the Sunlight angle. Think about this....when you look at other clouds (BTW, a contrail is merely a form of cirrus cloud)...when you look at clouds, depending on the angle of the Sun...do you ever see those clouds with "dark" sides? (Usually, closer to the ground, but again, depends on your angle of view).

THINK about it, please.

Adding....just as contrails, when viewed against a setting or rising Sun, low on the horizon, will appear "red". As ALL clouds will.

Recall a very, very old sailors' ditty:

"Red clouds at night, sailors' delight.
Red clouds in mornin', sailors take warnin'"

Please feel free to look that up on Google (or Search Engine of your choice). That ditty has variations, but they ALL make the same point. Please, THINK about it!