Flight attendants often post on social media to warn passengers against drinking the onboard coffee, claiming it’s made with water that isn’t clean enough.
A recent study supports their stance and identifies the U.S. airlines most likely to carry potentially unsafe water: passengers on American Airlines,JetBlue, and multiple regional airlines should be most wary, according to the research.
The study was conducted by the Center for Food as Medicine and Longevity, which analyzed results from 35,674 water tests. These tests were conducted by the airlines over a three-year period — October 1, 2022, through September 30, 2025 — and were officially reported to the Environmental Protection Agency (EPA) by the carriers.
The samples were collected from various aircraft points, such as galley faucets and bathroom sinks, and tested for coliforms, red-flag microbes that can indicate the presence of disease-causing organisms, and E. coli. This bacterium indicates fecal contamination and can cause stomach cramps, diarrhea, pneumonia, and other illnesses.
The researchers developed a scorecard for 10 major and 11 regional airlines based on factors including contamination levels, the number of violations per aircraft, and how often each carrier disinfected and flushed its aircraft water tanks.
In total, 949 samples (2.66 percent) tested positive for coliforms, and 32 (0.09 percent) tested positive for E. coli.
Among major airlines, American had the lowest score — 1.75 out of five, or a grade D. JetBlue, which also ranked lowest in a 2019 water safety study, scored 1.8 but was still graded a D.
Spirit was also graded D, but managed 2.05 out of five, while United, Hawaiian, and Southwest all received C grades.
Allegiant Air and Alaska both received B’s, while Delta and Frontier topped the table with A grades and scores of five out of five and 4.8, respectively.
The regional ranking was topped by GoJet, which scored 3.85 (grade B). Six carriers were graded D—SkyWest Airlines, Envoy Air, PSA Airlines, Air Wisconsin, Republic Airways, and CommuteAir, and Mesa Airlines an F, with a score of just 1.35 out of five.
Charles Platkin, PhD, director of the Center for Food as Medicine and Longevity, remarked: “Nearly all regional airlines need to improve their onboard water safety, with the exception of GoJet Airlines.”
Water used in galleys and bathroom sinks is drawn from a water tank on the plane, which airlines are required to disinfect and flush four times per year. Still, the study noted that aircraft water systems can experience periods of stagnation between flights and temperature variations during ascent and descent. No matter how careful an airline is, contamination can still occur from airport hoses and tanks.
What’s more, the number of bacteria breaches might be even higher, as researchers discovered a large number of incomplete EPA violation records, where the “end date” of the investigation was missing. These statistics were therefore not counted.
With this in mind, Platkin recommends avoiding drinking water on board and even water from bathroom taps.
He said: “Never drink any water onboard that isn’t in a sealed bottle and do not drink coffee or tea onboard. [In addition] do not wash your hands in the bathroom — use alcohol-based hand sanitizer containing at least 60 per cent alcohol instead.”
American Airlines said in a statement: “American’s potable water program is fully in compliance with the Environmental Protection Agency’s (EPA) Aircraft Drinking Water Rule (ADWR). A recent EPA audit showed there were no significant findings with our program, and we have not received any violations for any potable water cabinets or trucks that we use.
“Our team is closely reviewing the Center for Food as Medicine & Longevity’s analysis — including its methodology and whether it was peer reviewed — to determine any potential changes that would further enhance the safety and well-being of our customers and team.”
The Independent has reached out to JetBlue for comment.
Airline water safety scores
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)