Yes. The Chemtrails believers think that there's some sort of chemical being released by some/all planes in their contrails. Depending on how gaga they are, the cause is to either increase the planet's albedo and so "do things" to the weather, or that the chemicals are to poison us/contain mind control agents/do multifarious other "bad things".

It's all completely rubbish conspiracy theory nonsense, obviously, but you can't dissuade them because the conspiracy requires everyone who is in a position to notice the lack of big tanks of mind-control chemicals on planes is obviously part of the conspiracy and not to be trusted.

edit - as with all good woowoo theories, there is a grain of truth in there, though. Your bog-standard water-vapour and a little aviation fuel contrail does reflect more sunlight into space, and scientists have measured a quanitifiable decrease in the amount of light reaching the surface over the last fifty years as the number of flights (and particulate pollution in general) have increased. It has a net cooling effect on our atmosphere, and so has actually been unwittingly counteracting some of the global warming effects of CO2 pollution. Do a search for "global dimming" if you want to know more.