“I’ve seen instances when the blue sky, after a few hours, is laced almost completely in every conceivable direction, but mostly west to east, by jet contrails. By afternoon, the sky is clouded over as they spread out.
Utility companies, oil refineries, and smelters have built higher smokestacks, thereby causing their pollution to be deposited hundreds of miles away. That might cause some of the acid rain problem, but I think it is minimal in the final analysis.
The jet's exhaust is already up there and only has to have a change in atmospheric conditions to precipitate out as acid rain.” 
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