The term contrail is a contraction of condensation and trail, as chemtrail is of chemical and trail. The first one is used to name trails left in the sky by aircrafts under certain atmospheric conditions. Some people argue that when contrails do not dissipate quickly is because contain substances added and sprayed for sinister purposes undisclosed to the population (weather modification and biological and/or chemical war are the most common).

Exist various versions of the chemtrail theory, most of them propagated via the internet in discussions forums or websites, and to a lesser degree by the mass media such as TV and radio programs. The outspread popularity and diffusion of the theory has already become a reality. Scientific community has repeatedly rejected that chemtrails exist, insisting that are just contrails. We analyze this phenomenon.

We made a exhaustive literature review in Journals of Meteorology and Aviation, about the formation of condensation trails, in Social Pychology Journals about the genesis and dissemination of the chemtrails theory. Finally, we will make a brief presentation of documentation built around the theory of chemtrails in the province of Zamora (Spain), where is one of the most active spots in southern Europe.

official statements on the non-existence of chemtrails have not discouraged the proponents of the theory of chemtrails.

The authors have not supplied their declaration of competing interest.