Contrails can form through the addition of water vapor to the air from the jet engine exhaust.
Even tiny nuclei released in the exhaust fumes may be sufficient to generate ice crystals, and hence, condensation trails. The strange spray patterns are being reported repeatedly over towns in Tennessee, Connecticut, New Hampshire, New York, Nevada, Idaho, Mississippi, Montana, Oklahoma, Washington state and California. Immune system symptoms include swollen hands and legs, night fever and shortness of breath. A group of about a dozen researchers spent more than a year, mostly in secret, studying the chemtrails. The group poured over thousands of scientific, government and military documents, most of which can be found in the public domain but buried among countless papers in highly scientific web sites on the Internet.