For decades, commercial flights have established themselves as one of the safest ways to travel. However, a new Wall Street Journal (WSJ) investigation, based on more than one million reports from the Federal Aviation Administration (FAA) and NASA, thousands of internal documents, and more than 100 interviews with experts, has revealed a problem that has received little public attention despite years of complaints from crews and unions: the infiltration of toxic gases into commercial aircraft cabins.

Since 2010, the FAA has documented thousands of reports of “smoke incidents” on commercial aircraft. The WSJ analysis shows that the true frequency of these events will reach approximately 108 cases per million flights by 2024, a figure triple the 33 incidents per million that the FAA had estimated in 2015.

For its part, CBS News conducted an independent analysis of FAA reports and determined that more than three such incidents occur daily in the United States alone. Data reveals that Airbus accounted for around 61% of the smoke incidents reported last year, recording almost three times as many cases as Boeing aircraft.

Bleed Air System: The Source of the Problem on Aircraft

According to media reports, the origin of these events is no mystery to specialists familiar with aircraft design. The vast majority of modern commercial aircraft operate using a system called “bleed air,” which draws outside air through the jet engines, compresses and heats it before distributing it through the cabin to provide pressurization and air conditioning.

The downside is that this air can become contaminated when engine seals fail—something that happens more frequently as planes age—and allow oil and other fluids to leak in, vaporizing at high temperatures. The result is a mix of neurotoxins,Carbon monoxide and chemical compounds inhaled by both passengers and crew.

A landmark case occurred in February, when the cockpit of Delta Flight 876 filled with smoke during transit, forcing an emergency landing. Inspectors discovered that one of the plane's engine oil tanks had vaporized in the cabin.

The WSJ analysis showed that among the three largest U.S. airlines, Airbus A320s experience smoke incidents far more frequently than Boeing 737s—more than seven times more frequently. In contrast, the 787 Dreamliner, which does not have a bleed air system, does not appear in these statistics.

JetBlue and Spirit Airlines, which primarily operate A320s, saw a combined 660 percent increase in the frequency of fume-related incidents between 2016 and 2024, the WSJ found.

Health Effects: Neurological Symptoms

While brief exposure to these fumes typically does not reach toxic levels, prolonged exposure can lead to serious problems.

Dr. Robert Harrison, an occupational medicine specialist at the University of California, San Francisco, who has treated more than 100 flight crew members for toxic exposure and was also cited in the WSJ report, told CBS News, “The most common problems I see are general nervous system problems.”

“A person inhales [the fumes] into their lungs, These circulate through the body and then reach the brain, where they can affect other parts of the nervous system,” he explained.

Neurologist Robert Kaniecki, who has treated dozens of pilots and more than 100 flight attendants over the past 20 years for brain injuries related to smoke exposure, compared the effects on the brain to a “chemical shock.”

The doctor, who also consults for the Pittsburgh Steelers, found that these effects were “remarkably similar” to those experienced by National Football League (NFL) linebackers after taking a hard hit.

Faced with these alarming revelations, major players in the airline industry have responded with statements seeking to downplay concerns.

Airbus told CBS News that its planes “are designed and manufactured in accordance with all relevant and applicable airworthiness requirements” and that it is committed “to continually improving our products, working in close collaboration with operators and regulators to ensure the best possible cabin environment.”

For its part, the FAA maintains that it has “strict rules on cabin air,and studies have shown that cabin air is as good as or better than the air found in offices and homes.”

However, according to the WSJ, airplane manufacturers and airlines have not only downplayed the health risks, but have lobbied against certain safety measures and made harmful changes to cut costs.

Existing Solutions vs. Airline Industry Resistance

The technology to solve this problem already exists. The Boeing 787 Dreamliner has an alternative system that does not use bleed air, thus reducing the risk of smoke infiltration.

However, according to emails obtained by the WSJ, when Boeing executives were deciding how to market this new system, one executive expressed concern that talking about its benefits might draw attention to the poor air quality on the company’s existing planes.

The question then “remains”: If the problem is known, do technical solutions exist And if the incident rate continues to rise, why isn’t more forceful action being taken? As Sara Nelson, president of the AFA-CWA flight attendants union, told CBS News, “Every airplane should have a filtration system that prevents these toxins from entering the cabin.” Meanwhile, as the WSJ reported, a bipartisan bill recently reintroduced in Congress calls for the installation of specialized filters and the phasing out of bleed air, though a previous attempt was ultimately defeated after facing industry pushback last year. The next time you board a plane and notice an unusual odor, experts recommend paying attention. What may seem like a simple annoyance—reports describe scents ranging from nail polish to damp socks—could, recent research suggests, indicate contaminants in the cabin air. A phenomenon that studies show warrants closer scrutiny. Edited by Felipe Espinosa Wang with reporting from the Wall Street Journal and CBS News