How the Journal Reviewed Over a Million FAA Reports

Understanding the Hidden Issue of Engine Fumes in Airplane Cabins

The issue of engine fumes leaking into airplane cabins has long been a concern for passengers and crew alike, yet there is no public accounting of how frequently this occurs. The Federal Aviation Administration (FAA), airplane manufacturers, and airlines do not provide a transparent record of these incidents. However, The Wall Street Journal took it upon itself to investigate this critical issue.

Airlines are required to submit "service difficulty reports" (SDRs) to the FAA, detailing various operational problems they encounter during flights. These reports include identifying information about the aircraft and narrative descriptions of the issues. The Journal compiled a database of over one million SDRs, covering all accessible filings from 2010 through mid-2025. According to an FAA spokeswoman, these reports play a vital role in the agency’s safety surveillance system by helping identify trends, detect patterns, and spot potential risks.

To ensure a comprehensive analysis, the Journal focused on aircraft built by the three largest planemakers and flown by the top fifteen U.S. carriers by number of departures between 2010 and the first quarter of 2025. This approach allowed for a consistent comparison across different airlines and aircraft models.

Methodology and Validation

Journal reporters employed advanced techniques such as machine learning algorithms and large-language models, combined with manual review, to identify reports describing "fume events." In these cases, oil or hydraulic fluid contaminates the air supply, leading to fumes entering the cabin or flight deck. To validate their methodology, the team consulted experts and reviewed multiple studies, including one funded by the FAA, as well as internal documents from aircraft manufacturers and airlines.

The analysis followed a two-step process. First, reporters trained a statistical model using a list of classified SDRs compiled by Judith Anderson, an occupational health specialist at the Association of Flight Attendants-CWA union. Testing against 25% of Anderson’s data not used in training, the model correctly identified fume events 94% of the time. To reduce false positives, a prompt for a large language model was developed based on academic literature and aviation industry documents. Only reports classified as fume events by both methods were counted.

A 5% sample of each year’s reports revealed an error rate below 0.5%, with any errors found being corrected. To account for duplicate reports, multiple filings for the same aircraft and day were consolidated into a single event.

Trends and Findings

Using departure data from the Bureau of Transportation Statistics, the Journal calculated rates of fume events per airline and aircraft type. Their findings showed a significant increase in fume events, rising from about 12 per million departures in 2014 to nearly 108 per million in 2024.

The FAA attributed part of this increase to new guidance for reporting fume events, issued in November. However, the Journal’s analysis of fume event reports in December showed a count in line with previous years. Airlines and crews interpret reporting guidelines differently, leading to significant variations in fume event reports between carriers. Anderson’s research using internal airline data found that while one airline reported 70% of fume events to the FAA, another reported only 13%.

Since aircraft lack sensors, reporting relies on crew members noticing and documenting odors—a process prone to human error and changing awareness of contamination events.

Additional Validation and Industry Response

To further validate its findings, the Journal analyzed 15 years of NASA’s Aviation Safety Reporting System (ASRS) filings. Despite being voluntary and anonymous, these reports revealed a similar pattern: among about 3,700 ASRS reports related to smoke, fire, fumes, or odor, the proportion describing fume events specifically increased by nearly 70% when comparing 2010-2016 to 2017-2024.

Airbus aircraft contributed significantly to this rise—the manufacturer’s share of ASRS fume event reports increased from 32% in the earlier period to 57% in the later period. An Airbus spokesman stated that their aircraft are designed and manufactured according to all relevant and applicable airworthiness requirements.

While other news outlets have investigated toxic fume events, including 2020 reporting in the Los Angeles Times, the Journal’s analysis stands out as the most comprehensive, drawing from more than one million service difficulty reports.