Chemtrails
The persistent white trails left by aircraft at high altitude are condensation trails (contrails) made of ice crystals formed when hot exhaust meets cold, humid air. There is no scientific evidence of any covert large-scale atmospheric spraying program.
What we know
Contrails, short for condensation trails, are well-understood atmospheric phenomena. Jet exhaust contains water vapor, which freezes rapidly at high-altitude temperatures (typically below −39°C). Under conditions of high atmospheric humidity, contrails persist and can spread into cirrus-like clouds. This behavior was documented as early as World War II. NASA, NOAA, the EPA, and the FAA jointly published a fact sheet in 2000 explaining contrail science in response to public concerns.
A 2016 survey published in Environmental Research Letters asked 77 atmospheric scientists and geochemists specialising in contrails and atmospheric deposition whether they had encountered evidence of a secret large-scale atmospheric spraying program. Seventy-six out of 77 (98.7%) said they had not, and stated that the data cited as evidence, including persistent contrails, barium or aluminum detections, could be explained by normal atmospheric chemistry and contrail science.
The "chemtrails" theory typically claims that trails are made of chemical or biological agents dispersed for purposes including weather modification, population control, or mind control. No credible evidence has been produced to support any of these claims. The U.S. Air Force explicitly stated that the theory "has been investigated and refuted by many established and accredited universities, scientific organizations, and major media publications." The EPA states it is not aware of any scientific evidence supporting claims of nefarious activities related to contrails.
Some early-stage research into solar geoengineering (deliberately reflecting sunlight) exists at academic institutions, but this is open, published research, not a covert program. The visible contrails seen in everyday skies are composed of ice and water, and their behavior varies predictably with atmospheric humidity.
Common claims
- Persistent contrails are proof of secret chemical sprayingNot supported, contrail persistence is explained by atmospheric humidity levels
- Barium and aluminum found in soil/water prove chemtrailsNot supported, these elements occur naturally; cited analyses have contained errors
- Governments are poisoning the population through chemtrailsNo evidence, no regulatory agency, whistleblower, or confirmed sample has supported this
- Contrails never used to last this longFalse, long-lasting contrails are documented in photographs dating to WWII
Evidence hierarchy
All sources
- Atmospheric science experts agree chemtrails is a fantasyScience / AAAS · 2016
- Information on Contrails from AircraftU.S. Environmental Protection Agency · 2025
- Aircraft Contrails, NASA Earth ObservatoryNASA · 2004
- Coordinated Approach to Contrails Research, National AcademiesNational Academies of Sciences, Engineering, and Medicine · 2025
- Understanding and addressing chemtrails, Salata InstituteHarvard Salata Institute · 2025