therwol wrote:
From memory, the combustion of hydrocarbons produces carbon dioxide and water. Okay, some carbon monoxide and contaminant by products, but what you see in contrails is the water vapor. It may not be pure water, but it's the water condensing in the cold of high altitude that you see. Nothing has changed about this since planes have been able to fly high enough to cause the phenomenon. They don't have to be jets.