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Coffee or tea on a U.S. airline? Unless you're flying Delta, think again. That's the message from a 2026 airline water quality study, which ranked airlines according to five criteria: violations per aircraft, Maximum Contaminant Level violations for E. coli, indicator-positive rates, public notices, and disinfecting and flushing frequency. The study period was October 1, 2022 through September 30, 2025, with 5.0 the highest rating and 0.0 the worst.
- 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)
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Unfortunately, the Environmental Protection Agency (EPA) has been very lax in enforcing the federal government's Aircraft Drinking Water Rule (ADWR), which requires airlines to provide flight crew and passengers with safe drinking water. The ADWR mandates that airlines must sample their water tanks to test for coliform bacteria and possible E. coli. Airlines are also required to disinfect and flush each aircraft’s water tank four times per year. Alternatively, an airline may choose to disinfect and flush once a year, but if so, it must test monthly.
Unlike city water systems with regular monitoring, aircraft water systems are subject to periods of stagnation between flights, temperature variations during ascent and descent, and mechanical stress from aircraft operations. This makes aircraft water conducive to biofilm formation and microbial proliferation. Contamination introduced during the servicing process—whether from hoses, truck tanks, or improper handling—can persist in aircraft systems if adequate disinfection and flushing protocols aren't rigorously maintained.
The potential health consequences of consuming contaminated aircraft drinking water range from acute gastrointestinal illness to exposure to opportunistic pathogens. Vulnerable populations, including young children, elderly passengers, pregnant women, and immunocompromised individuals, may face elevated risks from waterborne pathogens.
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Takeaways
After security, fill your water bottle with filtered water at the airport or purchase bottled water to bring onboard, in order to have sufficient water for your flight. Onboard, drink bottled beverages and avoid unbottled aircraft tap water, coffee, and tea (especially when not flying Delta).
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Source: The Center for Food as Medicine and Longevity
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