Well, FWIW airplanes have been spewing chemicals into the upper atmosphere for decades. The important points are (a) it's not intentional except inasmuch as it has to be that way in order for the planes to fly, and (b) the chemicals are largely water, carbon dioxide, carbon monoxide, nitrogen oxides, and other products of the combustion of jet fuel.

This does does have an effect on the weather -- remember the three no-fly days after the WTC was destroyed? -- but again there was/is no sinister conspiracy trying to change the weather.

Fred

__________________
"For shame, gentlemen, pack your evidence a little better against another time."
-- John Dryden, "The Vindication of The Duke of Guise" 1684