We had this happen over Canton last year.
It was weird. Dozens of aircraft flying set patterns and forming a "net" of the trails.
The aircraft were too high to identify and by time I got better equipment to see them with it was too hazy.
I figured it was a military exercise and didn't worry about it. For a week afterwards the hospitals were filled with people complaining about breathing problems. Funny thing is, I probably have the worlds most vulnerable respiratory system and nothing happened to me - Never even thought about it until I heard about the hospitals being filled on the news.
It was cool to watch it. No clue what they were doing or why. Despite all the tinfoil hat theories floating around town, it was nothing more than a half hour of "wow, that's weird" .
Robb
Sorry, couldn't resist posting this one.