The United States Court of Appeals for the Seventh Circuit on 16 June 2026 affirmed summary judgment in favour of American Airlines (AA) and uniform manufacturer Twin Hill, ending a federal case originally brought by 70 employees over health problems they attributed to grey uniforms introduced in September 2016. The court found that the employees lacked admissible expert evidence establishing that the uniforms caused their reported symptoms. The ruling comes a full decade after American contracted with Twin Hill in February 2015 to supply new workwear for approximately 70,000 customer-facing employees — including flight attendants, pilots, and above-wing airport staff — and closes one of the largest occupational health disputes in US commercial aviation history.
The Seventh Circuit’s decision does not end all litigation over the uniforms. State-level lawsuits under the case name Poole v. Twin Hill remain active, and California juries have already returned significant verdicts. In 2023, a California jury awarded more than $1 million to four flight attendants. In 2025, a second California jury awarded $18.6 million to five flight attendants, assigning 90% of the fault to Twin Hill and 10% to American Airlines. The divergence between the federal and state outcomes reflects a fundamental difference in evidentiary standards — not a disagreement about what happened.
The Uniform Dispute Began After 2016 Rollout
According to the aviation publication View from the Wing, American Airlines contracted with Twin Hill in February 2015 to replace its legacy blue uniforms with a new grey range. The rollout began in September 2016. Complaints emerged before and around the launch date, covering a broad range of reported conditions: skin reactions, respiratory problems, eye irritation, neurological symptoms, gastrointestinal issues, and reproductive effects.
The Association of Professional Flight Attendants (APFA), which represents American’s cabin crew, reported 3,758 complaints from roughly 18,000 flight attendants. The National Institute for Occupational Safety and Health (NIOSH) broke that figure down as 3,686 symptom reports and 796 reports involving medical care. A further 47 employees said they experienced symptoms simply from being in proximity to the uniforms, without wearing them.
Employees also argued that American had been on notice before the rollout. Twin Hill had previously supplied uniforms to Alaska Airlines that generated comparable complaints from flight attendants in 2010 and 2011, leading to a class action lawsuit that Twin Hill ultimately won. Testing during the Alaska dispute had found low levels of tributyl phosphate (TBP), an endocrine disruptor used as a wetting agent in textile production, and Disperse Orange 37, a toxic dye banned in many countries that can cause skin and respiratory irritation. American Airlines’ pilots also reported rashes and other symptoms during a field test of the Twin Hill uniforms prior to the 2016 rollout — yet the airline proceeded with the contract.
In December 2016, APFA released a statement to members confirming it had received over 1,600 reports of suspected uniform reactions including headaches, rashes, hives, burning skin, eye irritation, and respiratory problems. The union demanded a full recall of the new uniforms.
Testing Found Chemicals, Uncertainties, And Inconclusive Results
American Airlines responded to the complaints by commissioning testing firm Intertek to examine 123 Twin Hill garments alongside legacy uniforms and off-the-rack retail clothing. Intertek identified potential sensitizers in the Twin Hill items but concluded it was unlikely those chemicals were uniquely responsible for the reported reactions — finding them within the normal range that would affect only those already sensitive to a given garment.
NIOSH, the federal government’s occupational health research body, found it was possible that textile chemicals contributed to skin symptoms in some employees, but was unable to identify a specific causative chemical. A 2018 study by the Harvard T.H. Chan School of Public Health — conducted after comparable findings at Alaska Airlines — concluded that it was unlikely a single chemical was the culprit, noting instead that “it’s likely to be a unique combination.” Testing identified TBP, heavy metals, biocides, and dispersion dyes suspected of being carcinogens in the affected uniforms.
The Association of Flight Attendants (AFA) — which represents regional carrier crews at PSA, Piedmont, and Envoy, who wore the same Twin Hill garments — separately sent 14 uniform garments for independent laboratory testing in February 2017.
Those garments had been manufactured in at least five countries: Bangladesh, China, Indonesia, Sri Lanka, and Vietnam. The AFA also noted that APFA had made multiple requests to Twin Hill for Material Safety Data Sheets for the uniforms’ chemical components, but received no cooperation from the manufacturer.
American Responded First Accommodation First, and Then Contract Termination
American Airlines did not recall the uniforms but quickly offered alternatives. Employees were permitted to resume wearing old uniforms or purchase off-the-rack substitutes. Internal call records showed approximately 2,000 to 2,500 contacts related to irritation and reactions during the period of peak complaints. In June 2017, the airline announced it would replace the Twin Hill uniforms by 2020, formally terminating its contract with the manufacturer and ultimately switching to Lands’ End as its uniform supplier. The new Lands’ End uniforms entered full service in 2020.
American’s decision to terminate a major supply contract, discard significant uniform inventory, and allow employees to wear civilian alternatives was cited by plaintiffs in state proceedings as evidence of the airline’s own acknowledgement that the uniforms posed a real problem. The airline, however, maintained that the uniforms had undergone testing and met accepted standards. Its spokesman said at the time that uniform materials were found to be “in line with normal standards” — a position that sat uncomfortably alongside the scale of employee complaints and the decision to exit the Twin Hill contract.
Why The Federal Case Failed
The Seventh Circuit’s ruling in June 2026 turned entirely on the question of admissible expert evidence. In April 2025, a district court had already issued summary judgment against the 70 employees, finding that the plaintiffs’ key expert witnesses did not meet the reliability threshold required under federal law, and that without those experts, the remaining evidence — testing results and complaint volumes — could not establish a causal link between the uniforms and the symptoms.
The governing legal framework is Federal Rule of Evidence 702, which since the Supreme Court’s 1993 ruling in Daubert v. Merrell Dow Pharmaceuticals, Inc. has required judges to act as gatekeepers, screening expert testimony for scientific reliability before it reaches a jury. Under Rule 702, an expert’s opinion is only admissible if it is based on sufficient facts or data, produced through reliable principles and methods, and reliably applied to the facts of the case. A 2023 amendment to the rule further reinforced that the proponent of expert testimony must demonstrate compliance with these requirements by a preponderance of the evidence. Courts cannot simply defer the reliability question to the jury.
One of the employees’ expert witnesses attempted to infer causation from the correlation between the uniform rollout and the spike in complaints, combined with testing that found irritants in the garments. That expert offered no theory explaining how a given dose of a specific chemical caused the specific symptoms reported. The Seventh Circuit found this insufficient. Correlation between a product change and health complaints — even at the scale observed here — does not substitute for the requirement that causation be established through a reliable, peer-reviewed methodology.
The employees also argued that the doctrine of res ipsa loquitur — meaning “the thing speaks for itself” — should allow a jury to infer defect and causation from circumstantial evidence alone, without identifying a specific chemical and dose. The Seventh Circuit rejected that argument. The court also held that the employees’ attempt to invoke an Illinois law doctrine allowing a prima facie defect showing when a product fails its intended function was misplaced in this context.
Why State Courts Reached A Different Outcome
The tension between the federal ruling and the California jury verdicts is not a contradiction — it reflects the design of the US legal system. California, Illinois, Pennsylvania, and a number of other states continue to use the Frye standard for expert testimony admissibility rather than the federal Daubert/Rule 702 framework. The Frye standard — which predates Daubert — requires only that a scientific method be generally accepted in the relevant field, not that it be tested, peer-reviewed, and methodologically demonstrated to the satisfaction of a federal judge acting as gatekeeper.
In California, juries applying state product liability law awarded $1 million to four flight attendants in 2023 and nearly $18.6 million to five flight attendants in 2025, finding that the uniforms had failed to perform as safely as an ordinary consumer would reasonably expect. The 2025 jury allocated 90% of the damages to Twin Hill and 10% to American Airlines. These verdicts were reached under a standard that allowed the jury to assess pattern evidence — many employees, same uniforms, same symptoms, same timeline — without requiring plaintiffs to isolate the precise chemical mechanism.
View from the Wing reported that attorneys in the California proceedings cited the 2018 Harvard study connecting similar complaints to Alaska Airlines uniforms as supporting evidence. The California jury was unconvinced by Twin Hill’s defence experts. The federal court in the Seventh Circuit case operated under a stricter gatekeeping framework and reached a different outcome on the same underlying factual record.
What This Case Reveals About Occupational Textile Safety
The uniform episode exposed a regulatory gap that has since become a focus of discussion in aviation labour circles. Airline uniform fabrics are not subject to specific Federal Aviation Administration or OSHA requirements. General consumer protection rules from the Federal Trade Commission and the Consumer Product Safety Commission apply, but no mandatory pre-market chemical testing regime governs fabrics used in airline workwear. This means that flight attendant unions have had to negotiate independent fabric-testing protections directly into their collective bargaining agreements to secure those rights.
The chemicals identified in testing — tributyl phosphate, formaldehyde-based wrinkle-resistance treatments, and reactive dyes — are documented irritants and sensitizers with known links to contact dermatitis, respiratory symptoms, and endocrine disruption in occupational exposure settings. The difficulty in this case was not that these substances are harmless, but that proving a specific causal chain from a specific chemical at a specific concentration to specific symptoms in a specific individual — under the scrutiny that federal evidentiary rules demand — proved beyond what the employees’ experts could reliably demonstrate.
NIOSH’s own report recommended that airlines increase flexibility in uniform accommodation requests and improve communication with employees who report symptoms. The report stopped short of declaring the uniforms definitively dangerous, but did not declare them safe either. That ambiguity — which drove a decade of litigation — remains unresolved at the federal level.
Parallel Developments At American Airlines
The uniform litigation closes against the backdrop of a broader period of change at American Airlines. As reported by aviospace.org, American suspended four nonstop routes from Los Angeles International Airport (LAX) between August and October 2026 amid rising jet fuel costs that pushed its projected 2026 fuel bill more than $4 billion above 2025 levels. Chief Financial Officer Devon May stated on the April 2026 earnings call that “the increase in jet fuel prices kept this from being a profitable quarter.”
On the product side, the airline has been investing in its passenger experience. American began a phased rollout of free high-speed Wi-Fi for AAdvantage members in early 2026 and became the first US carrier to enter commercial service with the Airbus A321XLR in December 2025, deploying the type on transcontinental premium routes. Those developments reflect the commercial priorities of a carrier focused on premium cabin revenue — a different chapter from the industrial relations turbulence that defined the uniform crisis.
The lawsuit itself demonstrated a more fundamental tension: an airline operating at enormous scale, mandating a uniform change across 70,000 employees, had neither the regulatory obligation nor the internal mechanism to catch a potential occupational health problem before rollout.