Is Your Onboard Coffee Safe? New Study Ranks U.S. Airline Water Quality

Warnings from flight attendants about the cleanliness of onboard water have been common. A new study now supports these concerns. The research identifies U.S. airlines most likely to have potentially unsafe water for passengers. The Center for Food as Medicine and Longevity conducted the analysis. It ranked 21 carriers based on their compliance with federal rules.

The 2026 Airline Water Study Findings

The Center for Food as Medicine and Longevity analyzed results from 35,674 water tests. These tests were reported by airlines to the Environmental Protection Agency (EPA). The data covered a three-year period, from October 1, 2022, through September 30, 2025. Samples were collected from various aircraft points, including galley faucets and bathroom sinks. The tests looked for coliforms and E. coli bacteria. Coliforms are microbes that can signal disease-causing organisms. E. coli indicates fecal contamination and can cause severe illness.

Researchers developed a scorecard for 10 major and 11 regional airlines. The score considered contamination levels and the number of violations per aircraft. It also factored in how often carriers disinfected and flushed their water tanks. In total, 949 samples (2.66 percent) tested positive for coliforms. Additionally, 32 samples (0.09 percent) tested positive for E. coli.

Major Airline Water Safety Scores

Delta Air Lines achieved the highest score with a perfect five out of five, earning an A grade. Frontier Airlines followed closely with a 4.8 score, also receiving an A. Alaska Airlines and Allegiant Air both received B grades. They were followed by Southwest Airlines, Hawaiian Airlines, and United Airlines, which all received C grades.

At the bottom of the major airline ranking were American Airlines and JetBlue. American Airlines scored 1.75 out of five, receiving a D grade. JetBlue scored 1.80, also earning a D. Spirit Airlines was also graded D, with a score of 2.05.

Regional Carrier Performance

Regional airlines generally showed a greater need for improvement. GoJet Airlines was the top-ranked regional carrier, scoring 3.85 (Grade B). Six regional carriers received D grades. These included SkyWest Airlines, Envoy Air, and PSA Airlines. Mesa Airlines received the lowest score overall, just 1.35 out of five, resulting in an F grade. Charles Platkin, PhD, the Center's director, noted that nearly all regional airlines need to improve their regional airline water safety.

Regulatory Context and Airline Response

Aircraft water systems are regulated by the EPA's Aircraft Drinking Water Rule (ADWR). This rule, effective since 2011, mandates that airlines provide safe drinking water. Airlines must disinfect and flush their aircraft water tanks four times per year. The study noted that water can still be contaminated. This can happen due to stagnation between flights or issues with airport hoses and tanks.

American Airlines stated that its potable water program is fully compliant with the ADWR. The carrier noted a recent EPA audit showed no significant findings. They also stated they had not received any violations for their water cabinets or trucks. The airline is reviewing the Center's analysis, including its methodology, to determine any potential changes.

Passenger Recommendations and Industry Impact

The study underscores the challenges of maintaining aircraft drinking water quality. The ADWR is a crucial part of the FAA's oversight of U.S. carriers. For global context, other bodies like EASA also monitor aircraft health standards. The study's director, Charles Platkin, advises passengers to be cautious. He recommends avoiding any tap water on the plane. This includes onboard coffee water and tea. Passengers should use sealed bottles for drinking. Furthermore, he advises using alcohol-based hand sanitizer instead of washing hands in the lavatory. This is a significant finding for all aviation stakeholders, including manufacturers like Boeing who design these systems. For more on this and other industry developments, visit our commercial aviation news section.

• The study analyzed 35,674 water samples over three years.
• Delta Air Lines and Frontier Airlines ranked highest among major carriers.
• American Airlines and JetBlue received the lowest scores among major carriers.
• The findings highlight the importance of the EPA's Aircraft Drinking Water Rule compliance.