Chemtrails?

Ok so lately i've been reading about 'Chemtrails' and i don't think im fully convinced on this one.
I'm a fairly strong believer in conspiracy theories especially regarding a New World Order regime etc, but im not really believing this one.

Basically people believe that the 'exhaust fumes' left in the sky from aeroplanes are actually chemicals that being released at high altitudes on the public, which may be ordered by a NWO group in a bid to reduce the population to fit in with there agenda.
If this was true, would someone who was in on the conspiracy have to be regulary updated on where they're spraying the chemicals, and therefore have to avoid these areas???
I think that these so called chemtrails are really just the contrails left from planes aka condesed water vapour from the sheer heat given off from the planes exhaust pipe.