So did the phenomenon of persistent contrails that eventually spread out and haze up the entire sky exist 10-15 years ago?

A lot of people including myself seem to not remember the skies like this, a lot of people notice how bad it is nowadays.

The second German sighting occurred on May 9, 1919, when a pilot flying over Berlin at about 26,000 feet noticed the generation of a cloud stream that extended for about forty miles behind his plane. This stream eventually spread out to form a cloud layer that was about 3,000 feet thick. The pilot saw a similar phenomenon two days later.

A few months later I witnessed the Battle of Britain taking place over my head in the July, August and September 1940. Being in SE London we had a grandstand view of the titanic struggle going on day aftr day with the intricate patterns of the contrails the most evident witness to the dog fights taking place.

So an airplane at great heights leaves behind it, stretching for endless miles, a visible "wake" composed of ice particles so tiny that they do not fall as snow but remain suspended in the air.

Photo taken by Jerry Cole, combat aerialphotographer in the 390th Bomb Group at Framlingham Air Base in England. He is looking for a print from the original negative he shot around January 1944 or before. It shows contrails of P-47's crossing each other in the background and a B-17 in the foreground.

The spreading out of jet contrails into extensive cirrus sheets is a familiar sight. Often, when persistent conditions exist from 25,000 to 40,000ft, several long contrails increase in number and gradually merge into an almost solid interlaced sheet.

Henry Wadsworth Hinkle, hired man down on the farm with Uncle Clarence and Aunt Martha, looked skyward a few days ago and was awed by the multiplicity of "vapor trails," as he called them. That's the old name. Now they are called contrails-short for condensation trails-resulting from the condensation of heat flowing from high-flying jet engines.

A 43-year-old novice sailor said today that he followed jet contrails over the Atlantic to help him navigate after his sextant was smashed six days out of Pymouth, England.

Then there is the matter of cloudiness. The familiar contrails often left by high-flying planes might persist for a long time under some conditions.

Often, after several clear days, high flying jets begin leaving condensation trails in the sky. These "contrails" are the result of the condensation of water vapor that accompanies engine combustion at high altitudes.

He occasionally looked out the window at the earth and noted geographical locations. "We're coming over Europe and I've never seen so many jet plane contrails in my life," he reported

Shore was no naïf; he recognized the irony of many of his images. One of the cleverest is "U.S. 97, South of Klamath Falls, Oregon, July 21, 1973," which depicts a desolate spot of road where a billboard displays a snowcapped-mountain scene — against actual mountains in the distance. The billboard image seems to emerge from the land itself. Along with a cattle gate and a sky with blown-out contrails, the billboard is a tired and shabby advertisement for America itself.

So did the phenomenon of persistent contrails that eventually spread out and haze up the entire sky exist 10-15 years ago?

This cloud formation is very similar to the process that occurs when you breath on a cold winter day and you can see your own breath in the form of a "cloud". You may have noticed that on some days this "cloud" you produce lasts longer than on other days where it quickly disappears. The length of time that a contrail lasts is directly proportional to the amount of humidity that is already in the atmosphere. A drier atmosphere leads to a more short-lived contrail, while an atmosphere that has more humidity will lead to longer-lived contrails. However, if the atmosphere is too dry, no contrails will form. Occasionally a jet plane, especially if ascending or descending, will pass through a much drier or more moist layer of atmosphere which may result in a broken pattern to the contrail, with it appearing in segments rather than in one continuous plume.

This stream eventually spread out to form a cloud layer that was about 3,000 feet thick. The pilot saw a similar phenomenon two days later.

The spreading out of jet contrails into extensive cirrus sheets is a familiar sight.

i took these pics in late may, the temps were reaching high 90's so that would be no humidity. why would contrails last so long in a low humid area, and not only that but start to form into man made clouds

From my view when taking these that seemed to be at very low altitude, i do not believe these planes were 30,000 ft in the air, they did not look to be on a cruise path. you could be right though