Airplane Water Is Gross—Here’s What a New Study Found

Jan 21, 2026 Lily Alsup

A major new analysis of airline water quality has sparked fresh concern about the safety of onboard drinking water, revealing wide differences in how well airlines maintain and manage their water systems. The findings have implications for anyone who’s ever ordered coffee, tea, or plain tap water at 35,000 feet.

The 2026 Airline Water Study, conducted by the Center for Food as Medicine and Longevity, evaluated more than 35,000 water sample locations on flights across the U.S. from October 1, 2022, through September 30, 2025. It ranked 10 major and 11 regional carriers based on a “Water Safety Score” from 0.00 (worst) to 5.00 (best), using criteria that include violations of maximum contaminant levels (especially E. coli), bacterial indicator rates, and maintenance practices like flushing and disinfecting.

According to the study’s author, Charles Platkin, compliance with federal requirements—which airlines must self-report—is just the baseline. The study’s goal was to go beyond minimal compliance to compare how airlines actually perform when it comes to water quality.

The Results:

Top Performers

Delta Air Lines: 5.00/5.00 — Grade A
Frontier Airlines: 4.80 — Grade A
Alaska Airlines: 3.85 — Grade B

These airlines scored well enough that researchers considered their onboard water to be relatively safe to drink.

Mid-Pack & Problem Spots

Southwest Airlines: Around 3.3 — 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 carriers showed similar variability, with GoJet Airlines earning the best regional water score and Mesa Airlines at the bottom with a failing grade.

What Contaminants Were Found?

During the three-year study, researchers found:

949 total coliform positive sample locations (about 2.66% of tests), indicating bacterial contamination.
32 E. coli violations, which are more serious because E. coli can signal fecal contamination and greater health risk.

While low levels of harmless bacteria don’t automatically mean unsafe water, the presence of E. coli is a red flag for potential pathogens that could cause gastrointestinal illness.

U.S. law requires carriers to comply with the Environmental Protection Agency’s Aircraft Drinking Water Rule (ADWR), which mandates regular testing for coliform bacteria, monthly or quarterly flushing and disinfecting, and reporting of results. However, enforcement appears weak: civil penalties for violations are rare, leading critics to say the rule lacks “teeth.”

Because aircraft water systems sit unused between flights, go through complex plumbing, and are filled from many ground sources, conditions may foster bacterial growth more easily than on the ground.

Should Travelers Be Worried?

Experts urge a balanced perspective: for most healthy adults, a sip of water or occasional coffee on a flight is unlikely to cause serious harm, even if bacterial indicators are present. But for vulnerable groups—young children, older adults, pregnant people, and those with weakened immune systems—contaminated water may pose greater risk.

Practical Tips for Flying

In light of the findings, health professionals recommend:

Stick with bottled water that’s sealed rather than tap water from onboard tanks.
Avoid coffee or tea made with airplane water unless you’re confident it was prepared with bottled water.
Use alcohol-based hand sanitizer instead of washing hands with airplane sink water.

More Transparency—and Better Oversight?

The study highlights a need for greater transparency and stronger enforcement of existing standards. Passengers expect—not just compliance with minimum rules, but consistently safe drinking water on flights. As one expert put it, “Compliance should be the floor, not the ceiling.”

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