Toxic Fumes at 35,000 Feet? New Incidents Raise Big Questions

Most commercial jets pressurize and ventilate the cabin with “bleed air,” which is air drawn off the engines and routed through the environmental control system.

If engine oil seals or hydraulic components leak, that air can carry contaminants into the cabin or cockpit. These “fume events” have been documented by crews and passengers for decades, and recent analyses suggest they are more common than many realize.

In April, British Airways Flight 216, a Boeing 777 traveling from Washington, D.C., to London, diverted to Boston after fumes were detected in the cabin following a possible bird strike, though no injuries were reported. Earlier this year, Delta Flight 876, a Boeing 717, returned to Atlanta just minutes after takeoff when smoke began filling the cabin, prompting an emergency response for the 99 people aboard.

And in August, Condor Airlines Flight 3665, a Boeing 757-330 flying from Corfu to Düsseldorf, reported visible smoke from one of its engines mid-flight, though passengers and crew were unharmed. These events underscore that , while not daily occurrences, continue to affect commercial flights around the world.

Investigations and peer-reviewed work identify compounds associated with oil or hydraulic leaks, including organophosphates such as tricresyl phosphate (TCP) and carbon monoxide. Exposure has been linked to acute neurological symptoms in crew and passengers. A report by the National Library of Medicine summarizes in-flight measurements and discusses susceptibility and recovery after exposure.

Because airlines and regulators do not publish comprehensive incident datasets, independent analyses have filled the gap. The Wall Street Journal reviewed more than one million FAA service difficulty reports and found an upward trend in likely fume events over the past decade, with rates rising across several fleets. The analysis used machine learning and manual review, and cross-checked patterns with NASA’s incident database.

Reported symptoms include headache, dizziness, cognitive slowing, vision disturbances, respiratory irritation, and in some cases longer-lasting neurologic complaints. Medical and occupational health literature continues to examine mechanism and risk, while flight attendant unions provide practical guidance on documenting exposure, seeking medical evaluation, and preserving evidence after a smoke or odor event.

Cabins lack certified real-time sensors that can identify the specific chemical profile of a fume event. Last week the FAA announced it has sponsored research on detection technologies and is following European research programs on cabin air quality.

European efforts include safety planning within the 2025 European Plan for Aviation Safety and dedicated research on the toxicity of contaminated cabin air.

Laboratory simulators, such as a 2025 Fraunhofer initiative, are being used to characterize contaminant behavior and aid sensor development and mitigation testing.

Regulatory scrutiny of aviation safety culture remains elevated this year. While not limited to cabin air, recent U.S. oversight actions and reviews keep pressure on manufacturers and operators to improve safety systems and reporting.

Separately, the National Academies launched a study to examine contaminants present during smoke and fume events and identify research gaps that can guide standards.

If you experience a strong odor, visible haze, or sudden symptoms during a flight, notify crew immediately. After landing, seek medical evaluation and document the flight number, seat, time, and symptoms. Union and airline guidance sheets outline steps for clinical follow-up and evidence collection that can help clinicians assess exposure.

Evidence indicates that fume events occur with nontrivial frequency on aircraft that use engine bleed air. Health effects can be significant for some individuals.

Research and policy work this year focus on better detection, clearer reporting, and engineering approaches that reduce the chance of contaminated air reaching the cabin.