The trails with the loops in them are from jets... more specifically, military jets. The loops are from the manuevers executed by the jet. Commercial airlines do not do loops Corporate jets do not do loops.
It would make sense to me then, in conjunction with another posters response.. that of course those trails would linger longer, as those jets are at a much higher altitude than other planes to be performing those manuevers in the first place.
Just because something LOOKS big, doesen't mean it's close.
What secret port would commercial planes be excreting compounds from anyway? If it were the fuel, there would be a long list of employees in on it and someone would have blabbed by now. If it were anything else, again, someone would have blabbed.
I'm not saying I don't believe in any conspiracy theories... I just pick and choose my theories