Delta upgrades APUs on more than 300 planes amid toxic cabin-air incidents

Delta Air Lines has begun upgrading auxiliary power units on more than 300 Airbus jets after reports of toxic cabin air sickening crew members and passengers, according to multiple outlets. The Wall Street Journal reported Thursday that the airline has been swapping out APUs on its A320-family planes since 2022, and Delta says the work is now about 90% complete. APUs provide electricity and cabin air when the main engines aren’t running and do not propel the aircraft.

Faulty APUs can leak oil into the aircraft’s airflow system, allowing fumes and odors to spread through cabins even when the units are not in use. Airbus has acknowledged the APU design as a leading factor in these incidents, though other engines on the plane can also leak oil. Toxic-air events have surged in recent years, particularly on Airbus A320-family jets, the Journal reported earlier this month. The fumes have been linked to brain injuries and other health problems among crew members and passengers, leading to diversions and aborted flights in some cases. Some pilots have needed oxygen masks during episodes, and passengers have described alarming symptoms, including feeling disoriented.

One JetBlue flight attendant developed a traumatic brain injury after inhaling fumes on a flight to Puerto Rico, describing the odor as distinctly “dirty feet.” A passenger on another JetBlue leg recalled feeling drugged after inhaling air from the vents during a separate incident. In February, a Delta flight on a Boeing 717 filled with thick white smoke, and an investigation later found that oil had leaked from an engine enough to nearly empty the reservoir. Three former JetBlue employees are suing several airlines and equipment suppliers over toxic-fume incidents dating from 2022 to 2024, arguing lasting health effects from exposure.

Internal industry data indicate it is difficult to determine the full scope of the problem because not all events are reported and airlines use different standards for alerting the Federal Aviation Administration. In the past, manufacturers and regulators have documented seal problems in APUs for decades. Honeywell and Pratt & Whitney, two of the biggest suppliers, have faced issues with APU seals on the A320-family models, and Honeywell rolled out an update in 2023 intended to reduce odor events. A similar APU design is used on Boeing 737s as well. American Airlines began upgrading Honeywell APU seals in April 2023.

Delta has declined to comment beyond noting that fume events are rare but taken seriously, pointing to safety as the airline’s priority. In a separate statement, Airbus said its aircraft meet regulatory requirements and that the company continues to work with airlines and regulators to improve cabin environments. Neither JetBlue nor the other named companies have publicly responded to the lawsuits, and Fox News Digital did not receive comment from the parties at press time.

Industry experts say upgrading older APUs can lower the risk of leaks but does not eliminate it entirely, since oil fumes can also enter the cabin through other seals or the air system. Airbus has proposed a long-term fix that would move the air inlet to the top of the aircraft, a change that could reduce odor events by about 85 percent but would be implemented only on new planes. The broader implication for safety oversight remains under review as regulators, manufacturers and airlines weigh next steps in cabin-air safety.

As the industry continues to grapple with these concerns, travel customers and crews are watching how quickly airlines can complete replacements and what additional measures might be adopted to mitigate exposure to fumes. The balance between fleet modernization, regulatory requirements, and real-world health outcomes will shape how the industry approaches cabin air safety in the coming years.