Ah yes chemtrails.. I've done research on this quite extensively. Technically, it's called geo-engineering. Obama talked about it one time. There are many active programs in place run by universities and the DoD. You can read the patents for yourself.

Extensive List Of Patents » Extensive List Of Patents | Geoengineering Watch

I'm not aware of any commercial airlines being involved though.

However, there is a lot of crap out there too. For example, the picture below shows "chemtrails" but those are actually fuel dump masts on a 707. I've written to these guys before telling them otherwise but they are dead set on being wrong. What a shame because if they were just slightly more objective, they would be doing a great public service. For example, the govt has released bacterial agents in NYC subway lines to check for propagation. Independent reports of the chemtrail crowd found them out. Although the govt admitted to it, it would've been nice if they obtained legal permission from citizens rather than using them as human guinea pigs.


Real picture... but it's just fuel dumping.