For me the jury is still out on the issue. Planes have produced contrails since the invention of the jet engine. Heck, for all I know propeller aircraft also produce contrails. I am skeptical as it would take a LOT of chemicals disbursed at high altitude to mix into the lower atmosphere enough to affect a person. 'They' would be better off putting it into gasoline or diesel fuel and let motorized vehicles spread it around. Or maybe They already are!
