Chemtrails Conspiracy Theory

Claim: The condensation trails ("contrails") left by aircraft are actually chemical or biological agents ("chemtrails") sprayed deliberately for purposes ranging from population control and weather modification to secret geoengineering programs.

Origins: Emerged in the late 1990s after a debunked 1996 U.S. Air Force research paper on hypothetical weather-control technology was misread as evidence of an active program.

Why it's false: Contrails are simply water vapor condensing and freezing around aircraft engine exhaust particles at high altitude — well-documented atmospheric physics known since early aviation. Their varying persistence depends on humidity and temperature, not chemical content. A 2016 survey of atmospheric scientists and geochemists found zero evidence of a secret spraying program; none had encountered data supporting it.

Status: Firmly rejected by atmospheric science; the term is now sometimes used loosely to also refer to real, publicly-debated solar geoengineering research proposals, which are unrelated to the original conspiracy claim.