We’ve all seen those white streaks that trail behind jets, creating streaks against the blue sky.
The lines are called contrails, short for contrails, and appear when water vapor condenses and freezes around an airplane’s exhaust, according to the University Corporation for Atmospheric Research.
At least that’s what the science says. In recent years, a growing number of people believe that these contrails are actually chemtrails – a well-established conspiracy theory that claims these trails are not actually condensation at all, but are instead chemicals sprayed by the government.
While the theory may sound far-fetched to some, chemtrails have become a common conspiracy both in the US and around the world, despite evidence to the contrary.
What is the chemtrails conspiracy theory?
The chemtrails idea has been around since 1996 and is largely rooted in an Air Force research paper from the same year, “Weather as a Force Multiplier: Owning the Weather in 2025.” It outlines a “future weather modification system to achieve military objectives” using “aerospace forces,” and “does not reflect current military policy, practice, or capabilities,” the Environmental Protection Agency has stated.
Essentially, the chemtrails conspiracy theory states that contrails are not created by water vapor at all, but are instead a sign that the government, the wealthy, or a combination of both, are releasing toxic chemicals into the air, causing these white lines.
Ideas about the purpose of these so-called toxic chemicals vary. Some believe the chemicals are used to poison humanity, others say it’s for mind control, and some think it’s a way for the government to control the weather.
There isn’t a single official version of the theory, says Sijia Xiao, a doctoral candidate at the University of California, Berkeley, who conducted a 2021 study examining the chemtrails conspiracy theory and interviewing 20 believers and former believers. Instead, “individuals pick and choose aspects that resonate with them, blending personal interpretations or selectively adopting parts of the theory.”
How did the chemtrails conspiracy theory get started?
The idea that the government is spraying humanity with chemicals is not entirely unfounded.
According to researchers, the British government carried out more than 750 mock attacks on the general public during the Cold War. This exposed hundreds of thousands of people to zinc cadmium sulfide, a chemical chosen for its small size (similar to that of germs) and because it glows under ultraviolet light, making it easy to track. The chemical was thought at the time to be non-toxic, although repeated exposure could be carcinogenic. The US did the same in the 1950s and 1960s, using the chemical as a tracer to test the proliferation of biological weapons.
Although these tests took place decades ago, the theory has blossomed—so much so that in 2016 the EPA published a fourteen-page document explaining contrails, detailing the chemicals used by the Air Force, and attempting to dispute the conspiracy .
In 2021, a Facebook post went viral claiming that President Joe Biden “manipulated” the weather via chemtrails and caused Texas’ week-long deep freeze in February — with hundreds of people engaging with the message.
On X, thousands of people follow accounts dedicated to tracking and posting evidence of these chemtrails. A 2017 survey, with a nationally representative sample of 1,000 people, found that about 10% of Americans “completely” believed the conspiracy, while more than 30% of Americans found it at least “somewhat” true.
Belief in conspiracies can often be traced back to the skepticism of authority figures, Xiao said, and social media has also played a role in exacerbating the problem.
The algorithmic structure of social media ensures that people see information that reinforces their existing beliefs. Ex-believers interviewed attributed their continued faith in part to the “tremendous amount of pro-conspiracy information” on their social media feeds, said Coye Cheshire, a UC Berkeley professor who studies social psychology who was also involved in the research with Xiao. Scientific evidence debunking the theories simply wouldn’t make it into their feeds or into their social groups. Even if that were the case, other believers will only reinforce the theory.
The malleable nature of the conspiracy theory contributes to its power, Cheshire said.
“As some believers told us, the power of the conspiracy is that it can be adapted to new information, as the ‘smoking gun’ evidence never seems to arrive,” Cheshire said. “For example, even if believers are unsure that so-called chemtrails are actually being used for population control, the narrative can easily shift to weather manipulation and climate change without the need for new information or evidence.”
There is also the simple fact that we can see the contrails with our own eyes. Their visibility and presence in everyday life further fuels interest in the theory, Xiao added.
“Chemtrails have been the most interesting conspiracy because it is right in front of us and we still choose to ignore it,” one believer told Xiao and Cheshire.
While the theory may seem silly to some, believers’ underlying concerns stem from “legitimate social and environmental issues that deserve attention,” Xiao said. Distrust in government, concerns about environmental issues, or even the fight against chronic diseases can all lend credence to the chemtrails theory, suggesting that something else is causing these societal problems.
Are chemtrails real? Here’s what experts said
Scientists have said there is no evidence for the existence of chemtrails. Even if there were a government conspiracy at work in aircraft contrails, such a large-scale program would be difficult to cover up given the number of people that would be needed for the operation, Harvard researchers noted.
Scientists around the world have conducted studies that debunk the chemtrails conspiracy theory, detailing the existence of contrails and their variants. Even Edward Snowden, the whistleblower who leaked classified information from the National Security Agency, has declared that chemtrails are ‘nonexistent’.
Yet believers are not convinced. Belief in the theory has become so strong that meteorologists around the world have reported an increase in harassment and threats, usually after extreme weather, especially from conspiracy theorists who accuse them of hiding information.
“The collective agreement within these communities often trumps the rational dissent of scientists,” Xiao said. This makes it “extremely difficult for factual corrections to change these deeply held beliefs.”
For more CNN news and newsletters, create an account at CNN.com