From Simple English Wikipedia, the free encyclopedia
A Boeing 747 leaving a contrail.

A contrail (condensation trail) is a cloud-like trail of water vapor or ice crystals left by an airplane. When jet fuel burns, it produces water vapor and carbon dioxide. The water vapor condenses (turns from gas to liquid) because of the low temperature at the high altitude that the plane is flying. The chemtrail conspiracy theory claims that these trails may contain harmful chemicals being sprayed by government organizations.