Chemtrail refers to the trail of condensation, or contrail, left by jet engine exhaust when it comes into contact with the cold air at high altitudes. They form due to the high amounts of water vapor found in the exhaust. They are composed of tiny water droplets and ice crystals.
Chemtrails form in altitudes above 26,000 feet in temperatures below minus 40 degrees Fahrenheit when the relative humidity is over 60 percent. The word chemtrail is an amalgamation of the words chemical and trail. It is associated with conspiracy theories involving contrails. These theories espouse notions that condensation trails consist of chemical agents being deliberately released into the atmosphere by government agencies.