Think That Coffee’s Safe on a Plane? Think Again, Researchers Say

Maybe stay away from the airplane water—depending on which flight you’re on. A recent report finds that some airlines do a much worse job of keeping their drinking water sanitary than others.

Researchers with the Center for Food as Medicine and Longevity examined water sample data collected by the Environmental Protection Agency. Some airlines ranked high in consistently having onboard water free of potential foodborne bugs such as Escherichia coli, but many others were middling to plain awful. The EPA could also be doing a better job, the researchers say, namely by punishing airlines that regularly flout the rules.

The safest water to drink while flying

In 2011, the EPA established the Aircraft Drinking Water Rule (ADWR), a regulation intended to modernize and improve the quality of drinking water provided during flights, which is typically sourced from tanks in both domestic and international stops.

As part of the rule, airlines are required to regularly test their water for certain microorganisms. These include coliform bacteria, a broad group of microbes that can not only sicken people but also tend to signal the presence of other germs found in human feces. The tests can also screen for E. coli, a specific species of coliform bacteria that’s a common cause of foodborne illness.

Airlines are additionally required to provide evidence that they perform routine safety measures, such as disinfection and flushing, and that they take corrective action when their planes are found to have failed safety checks.

The Center’s airline rankings. © Center for Food As Medicine and Longevity

The Center’s Airline Water Study focuses on 10 major and 11 regional airlines operating in the U.S. The researchers analyzed EPA data collected from these airlines between October 1, 2022, and September 30, 2025. They used several metrics to come up with their rankings, scored from 0 to 5, which are also presented as letter grades. These criteria included the total number of violations per aircraft, public notices, the amount of violations from having too much E. coli in their water, and how often airlines cleaned their water.

Only one airline earned a perfect 5.0 score, the researchers found: Delta Airlines. Frontier Airlines was the only other to score an A, with a total score of 4.80, and Alaska Airlines was third with a B score of 3.85. Of the major airlines, American Airlines was the worst-performing, with a D score of 1.75. Just about every regional airline fared badly, with only one scoring a B (GoJet Airlines).

“Nearly all regional airlines need to improve their onboard water safety, with the exception of GoJet Airlines,” said Charles Platkin, director of the Center for Food as Medicine and Longevity, in a statement released by the non-profit organization.

What to do

There does seem to have been some improvement since 2019, when a similar study of airline drinking water was conducted by Platkin and others. Delta Airlines notably rose from a near-rock-bottom score of 1.6 in the years since. But others, like JetBlue, continued to have floundering scores. And the researchers note that EPA still only rarely levies civil fines at airlines that regularly violate ADWR regulations.

Given the findings, the Center says that flight goers shouldn’t drink any water not given in a sealed bottle if possible, shouldn’t drink coffee or tea made with onboard water, and should even avoid using airplane water to wash their hands (instead, they should use hand sanitizer with at least 60% alcohol).

Personally speaking, I’m definitely going to be a bit more cautious about what I drink on a plane.