I would also like to start a topic on chemtrails as I have been researching the topic for some time, and I have an opinion with some evidence to support it. Before gong into it, what are your strongest points against or for it. I will join you later, once you have come up with your ideas.
AB, that photo of the two planes...I assume your research has enlightened you as to aircraft separation rules at flight levels, yes? Two planes in close lateral distances travelling in the same direction will be separated by at least 2000 feet. Your two jetliners in the photo were so separated...you won't find airliners doing formation flights like you imply. (~100m separation). This vertical separation would also explain any differences in contrail appearances...as would differences in aircraft types, weights, power settings, engine types, local atmospheric conditions and other variables. Who knows, maybe one is a 737 and the other is a more distant 767. And the telephoto lens does distort/compress the apparent distance between the aircraft.
You said you have some "evidence to support it" (chemtrails). Still waiting for that evidence. I suspect that the increase in contrails can be significantly explained by the increase in the number of airliners flying up there, aka "fragmentation". More smaller jets flying vs fewer heavies, this in order to cater to customer demands for more convenient flight schedules. Air traffic continues to increase, and it has only recently become a topic for the CTs.
Finally, no one to date has ever made a direct correlation between contrails and any materials (natural or otherwise) found on the Earth's surface. There was a site collecting funds to capture "chemtrail" evidence directly via a business jet, but after some fundraising, the site closed down, much to the consternation of the gullible contributors.
How about you show us your best evidence (aside from "it looks strange to me"). I still rarely see contrails here in Colorado (the "mountain west"), likely a RH issue at altitude, though we do sometimes get the "dashed" trails due to the jetstream interacting with the mountain wave effect. When I do see trails, and I have access to the internet, flightaware.com makes it easy to ID the flights (even shows their filed flightplans). Oft times, one can easily ID the flights visually. Had a Virgin A380 going over some time back, conning all to hell and gone...beautiful sight! Heavy 747s are pretty as well.
Contrails are a natural byproduct of aircraft flying in the right conditions, which can even be on/near the ground. Show us some concrete evidence to the contrary, all those pretty youtube videos aren't doing it.