From Shado:
"I took these photos on Thanksgiving afternoon. The planes (eventually 5 were visible) continued their aerosol spraying well into the night. The trails were visible in moonlight which became very hazy as the trails built up. This has been going on in Chicago for about the past two years. Sometimes the planes disappear for a week or two at a time, then return for 3 to 4 days in a row. The "trail_compare" photo shows a normal contrail of a regular jet in the same section of the sky as the chemplanes."

(Well! Talk about Synchronicity - I was outside on Thanksgiving Day when I happened to look up at the sky and saw pretty much "This" right over my head. I couldn't believe it. It had been a clear, blue day with visible plane traffic (it's the busiest air traffic day of the year, They say) but not one trail in the sky except for the occasional "sky scrapers" way high up there leaving a thin white line that disappeared as fast as it was made. Then all of a sudden They show up and start blanketing the sky in a blitz that was like a feeding frenzy. In the course of about 3 hours the sky was soup. I was so mad I didn't have a camera - and then Shado sends these pics. Scary someone out there is thinking like I am! :) They must have been right where I was because this is exactly what I saw, too. Repeat after me - these are just normal airplane contrails of water vapor...it's just Uncle Mike and Aunt Syl flying in the 747....nothing going on here....these are all over 29,000 feet...you people are imaging all this...you won't feel like you have the flu tomorrow ....(Thanks Shado!)