The truth behind those white streaks trailing behind jets in the sky

Aircraft contrails in the sky at dawn in London. Many people believe these contrails are actually dangerous or being used for conspicuous purposes. (Toby Melville / Reuters via CNN Newsource)

We’ve all seen those white streaks trailing behind jets, creating stripes against the blue sky.

The lines are called contrails, short for condensation trails, and they appear when water vapour condenses and freezes around the exhaust from an aircraft, according to the University Corporation for Atmospheric Research.

At least that’s what science says. In recent years, a growing number of people believe that these contrails are actually chemtrails — a well-established conspiracy theory asserting that these trails aren’t made from condensation at all, but are instead chemicals being sprayed by the government.

Though the theory may sound far-fetched to some, chemtrails have become a common conspiracy both in the U.S. 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 capability,” the Environmental Protection Agency has stated.

At its most basic, the chemtrails conspiracy theory posits that contrails are not created by water vapour at all, but instead are a sign that the government, the wealthy, or some mix of the two, is secreting toxic chemicals into the air, creating these white lines.

Ideas about the purpose of these supposed toxic chemicals vary. Some believe the chemicals are being 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’s no single official version of the theory, said Sijia Xiao, a PhD candidate at the University of California, Berkeley, who conducted a 2021 study exploring the chemtrails conspiracy theory and interviewing 20 believers and former believers. Instead, individuals “pick and choose aspects that resonate with them, mixing in personal interpretations or selectively adopting parts of the theory.”

How did the chemtrails conspiracy theory take off?

The idea that the government is spraying humanity with chemicals isn’t completely without base.

During the Cold War, the British government conducted more than 750 mock chemical warfare attacks on the general public, according to researchers. This subjected hundreds of thousands of people to zinc cadmium sulfide, a chemical chosen due to its small size — it’s similar to that of germs — and because it glows under ultraviolet light, making it easy to trace. The chemical was thought to be nontoxic at the time, though repeated exposure could be cancerous. The US did the same in the 1950s and 1960s — using the chemical as a tracer to test the dispersion of biological weapons.

Though these tests were decades ago, the theory has flourished — so much so that in 2016, the EPA published a 14-page document explaining contrails, outlining 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 through chemtrails and caused Texas’s week-long deep freeze that February — with hundreds of people engaging with the message.

On X, thousands of people follow accounts dedicated to tracking and posting proof of these chemtrails. One 2017 study, which had a nationally representative sample of 1,000 people, found that about 10 per cent of Americans believed the conspiracy “completely,” while upwards of 30 per cent of Americans at least found it “somewhat” true.

Belief in conspiracies is often traced back to skepticism of authority figures, Xiao said, and social media has also had a role in magnifying the problem.

Social media’s algorithmic structure means people see information that reinforces their existing beliefs. Ex-believers interviewed attributed their ongoing belief in part to the “sheer amount of pro-conspiracy information” on their social media feeds, said Coye Cheshire, a professor at UC Berkeley studying social psychology, who was also involved in the study with Xiao. Scientific evidence debunking the theories simply wouldn’t make it onto their feeds or in their social groups. Even if it did, other believers will only reinforce the theory.

The malleable nature of the conspiracy theory helps give it strength, said Cheshire.

“As some believers told us, the power of the conspiracy is that it can be adjusted to fit any new information since the ‘smoking gun’ evidence never seems to come,” Cheshire said. “For example, even if believers are not sure that the so-called chemtrails are actually being used for population control, the narrative can easily shift to weather manipulation and climate change without requiring any new information or evidence.”

There’s also the simple fact that we can see the contrails with our own eyes. Their visibility and presence in everyday life helps draw even more interest to the theory, Xiao added.

“Chemtrails have been the most interesting conspiracy, because it’s right in front of our face and we still choose to ignore it,” one believer told Xiao and Cheshire.

Though the theory may seem silly to some, the underlying concerns of the believers come from “legitimate societal and environmental issues that warrant attention,” Xiao said. Distrust in the government, concerns about environmental issues, or even struggles with chronic illnesses can all lend credibility to the chemtrails theory, suggesting that something else is causing these societal issues.

Are chemtrails real? Here’s what experts have said

Scientists have said there is no evidence for the existence of chemtrails. Even if there was a government conspiracy at work in aircraft contrails, such a large-scale program would be difficult to cover up given the number of people who would be necessary for operation, Harvard researchers noted.

Around the world, scientists have conducted investigations debunking the chemtrails conspiracy theory, describing the existence of contrails and their variances at length. Even Edward Snowden, the whistleblower who leaked classified information from the National Security Agency, has stated that chemtrails “are not a thing.”

Still, believers are not convinced. Belief in the theory has become so strong that meteorologists around the world have reported an uptick in harassment and threats, usually after extreme weather, particularly from conspiracy theorists accusing them of hiding information.

“The collective agreement within these communities often overpowers the rational dissent of scientists,” Xiao said. This makes it “exceedingly difficult for factual corrections to alter these deeply entrenched beliefs.”