I’ve flown many times without a single care over the quality of water in my coffee, or concern over how sanitary it is to splash water over my hands and face. A new study makes it clear: that care may need to be elevated. An analysis, run by the Center for Food as Medicine and Longevity, ranks 10 major and 11 regional airlines on the safety of drinking water aboard flights. The results show that many airlines have reached “unhealthy” levels, according to the report.
“Airlines often respond to our findings by saying they comply with EPA guidelines,” says Charles Platkin, PhD., JD, MPH, director of the Center for Food as Medicine and Longevity, and the author of the study. “But the public should understand that all of this data is self-reported by the airlines, and enforcement depends on their accurate reporting and follow-through,” Platkin says. “Compliance should be the floor, not the ceiling.”
Violations for too-high levels of E. coli, a bacteria found in the intestines of humans and animals linked to the contamination of food or water, the strongest downward driver of airline scores.
How the Study Was Conducted
The three-year-long study, that ended on September 30, 2025, used a scoring system (5.00 to 0.00) and criteria that includes violations per aircraft, maximum contaminant level violations for E. coli, indicator-positive rates, public notices, and disinfecting and flushing frequency, to assess each airline to give it a water safety number.
(Note: A score of 3.5 or more indicates water aboard that is relatively safe to consume.)
To note, this study has not been published or peer-reviewed.
The Findings
Major Airlines
Delta Air Lines: 5.00 (Grade A)
Frontier Airlines: 4.80 (Grade A)
Alaska Airlines: 3.85 (Grade B)
Allegiant Air: 3.65 (Grade B)
Southwest Airlines: 3.30 (Grade C)
Hawaiian Airlines: 3.15 (Grade C)
United Airlines: 2.70 (Grade C)
Spirit Airlines: 2.05 (Grade D)
JetBlue: 1.80 (Grade D)
American Airlines: 1.75 (Grade D)
Regional Airlines
GoJet Airlines: 3.85 (Grade B)
Piedmont Airlines: 3.05 (Grade C)
Sun Country Airlines: 3.00 (Grade C)
Endeavor Air: 2.95 (Grade C)
SkyWest Airlines: 2.40 (Grade D)
Envoy Air: 2.30 (Grade D)
PSA Airlines: 2.25 (Grade D)
Air Wisconsin Airlines: 2.15 (Grade D)
Republic Airways: 2.05 (Grade D)
CommuteAir: 1.60 (Grade D)
Mesa Airlines: 1.35 (Grade F)
Should the Public Worry?
If you or your loved ones are part of a vulnerable population—young children, older adults, pregnant individuals, and people with weakened immune systems—these findings could be cause for concern, according to Don Thushara Galbadage, MPH, Phd, a professor of applied health sciences at Texas Christian University.
“For most healthy adults, drinking water, coffee, or tea on a flight is unlikely to result in serious illness,” Galbadage says. “Low-level bacterial findings, such as total coliforms, do not automatically mean the water is dangerous. However, the detection of certain indicator bacteria, particularly E. coli, can signal contamination that increases the risk of gastrointestinal illness.”
But for vulnerable populations, “even a mild gastrointestinal illness can have more serious consequences,” Galbadage says.
Scott M. Bartell, PhD, and professor of environmental and occupational health at the University of California, Irvine, highlights that we don’t actually know which types of contaminations they are, though. “The presence of coliforms could just be from a little harmless soil or plant material, or it could indicate something like biofilms or fecal contamination that can cause serious health problems,” he says.
Many of these airlines are detecting them in over 5% of samples, which Bartell points out is the federal limit for tap water. “The fact that several airlines are still seeing occasional E. coli detections, indicating fecal contamination, is very disturbing.”
Accountability vs. Reality
Really it all comes down to how well airlines manage and monitor their onboard drinking water systems, Platkin, Galbadage, and Bartell agree, indicating that this isn’t an overall health crisis.
The United States does regulate aircraft drinking water through the EPA’s Aircraft Drinking Water Rule, which requires airlines to disinfect, flush, and routinely test onboard water systems and report those results.
However, unlike city water, aircraft water systems face unique challenges like: stagnation between flights, temperature variations during ascent and descent, and mechanical stress from aircraft operations, the study states. Furthermore, the water passes through “relatively complex plumbing systems” when transported from airport facilities, Galbadage says. Every step of the way introduces room for error and conditions in which bacteria can grow.
“Federal public health agencies have long recognized that aircraft potable water systems require careful oversight,” says Galbadage.
This is the oversight that the Center for Food As Medicine and Longevity wants to see tightened.
“The ‘Shame on You’ Award goes to the EPA for weak enforcement,” Platkin says. Civil penalties for ADWR violations remain extremely rare if at all, the study states.
How to Fly Smarter
The CDC advises travelers to use precautions like using bottled water, avoiding beverages made with untreated tap water, and using
alcohol-based hand sanitizer rather than relying solely on sink water.
“I bring my own water bottle on flights, and fill it at one of those stations once I’m past security screening,” Bartell says. Note: Make sure the filter indicator light is green or yellow. Red means it’s time for a filter change. And if you want a coffee or tea, buy it before boarding, Bartell adds.
It’s possible bottle water is used for coffee and tea on flights, but there’s no way to know for sure.
“Passengers should be able to drink a cup of coffee or tea without hesitation, wash their hands with confidence, and trust that clean, safe water is available throughout their flight,” Platkin says. “These aren’t luxuries; they’re basic expectations. And while getting someone safely from point A to point B is essential, how passengers are treated during that journey matters too.”
The Bottom Line
“It is important for readers to understand that this report is not a peer-reviewed health risk assessment,” Galbadage states. “It compiles existing compliance and testing data into a comparative scorecard, which can be useful for transparency and accountability, but it does not directly measure individual exposure or predict health outcomes.”
But the study does reinforce a long-standing public health message, Galbadage says. Aircraft drinking water is less predictable than tap water. “Travelers who want to be cautious have straightforward ways to reduce potential risk.”
You can read the study in its entirety here.
“Airlines should focus not only on meeting minimum requirements, but on doing better and showing greater care for the people they serve,” Platkin says. “Passengers deserve that.”
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