Yeah, and I suppose they were doing those "chemtrails" when they dropped a Douglas Skyrocket from a modified B-29 over the desert SouthWest of the USA, 'way back in the 1950s. Nothing like wasting that chemical stuff over large uninhabited deserts, to prove it works, right?
As with the jet engines, the exhaust has to cool a bit, before the water vapor can become visible as a contrail. Contrails were seen all over England and Europe in WWII, from propeller-driven planes. Those guys were fighting for their lives; I doubt that anybody was doctoring their fuel for unproven social experiments, 'way back then.
Had a guy in the LZ telling me about them "chemtrails" late one day. An airliner went by high overhead, and one contrail was lit by the setting sun, so it was reddish in color. The other contrail, shaded by the red one, had no red light on it, so only the blue sky showed through. One contrail was red, one was blue; it was very plain to see.
"There, right up there, man! What do you call that, if those are not "chemtrails?"
I told him "I call that 'Sunset.'
Hey, at least we know the drinking water is still okay, right?
In case anybody is actually wondering, modern spray heads put out a much finer spray of droplets, in an effort to slow the flow-rate of the sprinklers, as compared to the the older sprinkler heads. These finer sprays make much better rainbows.