Disgusting study reveals which airline has filthiest drinking water… with e.coli found in some samples

Drinking water served aboard some of America’s most trusted airlines could be very bad for your health, after a study found some of it contained the dangerous e.coli bacteria. 

The Center for Food as Medicine and Longevity conducted a three-year study from October 1, 2022, to September 30, 2025, across 21 airlines, including 10 major airlines and 11 regional carriers.

Shockingly, the results found 32 instances of e.coli present, indicating that disease-causing pathogens could be present in the water systems aboard several airlines.

Each airline was assigned a Water Safety Score based on five areas: violations per aircraft, Maximum Contaminant Level violations for e.coli, indicator-positive rates, public notices, and disinfecting and flushing frequency.

Airlines were graded on a scale from 0.00 (lowest safety) to 5.0 (highest safety), based on the results of the tested criteria. Scores below 3.5 received letter grades of C, D, or F.

The majority of the major airlines scored below 3.5, but at the very bottom of the group was American Airlines with an abysmal 1.75. 

American Airlines carried the 151.7 million passengers in 2025, more than any other airline and holds the title of the world’s largest flight company, according to Simple Flying. 

Popular airline JetBlue did not fare much better, earning the second-lowest grade in the group, a 1.80.

Results of the study showed 32 violations of e.coli, indicating that disease-causing pathogens could be present in the water systems aboard several airlines

Regional airlines did not fare well, with only one regional company receiving a letter grade of a B [3.85].

‘Nearly all regional airlines need to improve their onboard water safety, except GoJet Airlines,’ says Charles Platkin, director of the Center for Food as Medicine and Longevity.

The study took 35,674 water sample locations for coliform bacteria testing, which resulted in 949 positive samples (2.66 percent). 

Since 2011, the federal Aircraft Drinking Water Rule (ADWR) requires airlines to provide passengers and flight crew with safe drinking water.

‘Delta Air Lines and Frontier Airlines win the top spots with the safest water in the sky, and Alaska Airlines finishes No. 3,’ said Platkin.

Delta Airlines was the only airline to receive a perfect score of 5.0, with close second Frontier Airlines at 4.80. Alaska Airlines was given a 3.85.

Despite praising certain companies, the study still advised three things never to do while aboard a plane: ‘NEVER drink any water onboard that isn’t in a sealed bottle.’

‘Do not drink coffee or tea onboard.’

‘Do not wash your hands in the bathroom; use alcohol-based hand sanitizer containing at least 60% alcohol instead.’

American Airlines, the most popular airline company in the world, had the lowest score among major companies [1.75]

Delta Airlines was praised by the study and was the only airline to receive a perfect score of 5.0

The ‘bottom-line’ advice was given as a precaution for passengers, just to be extra safe.

The study gave the US Environmental Protection Agency (EPA) a ‘Shame on You’ award because it is also responsible for enforcing aircraft water safety standards.

Civil penalties for airline water violations remain extremely rare, ‘if at all,’ the report added.

The study noted that because aircraft fly to numerous destinations, drinking water may be pumped into their tanks from sources that may not meet quality standards.

In addition, water quality also depends on the safety of the equipment used to transfer the water, such as trucks, water cabinets, carts, and hoses.

Airline Water Safety Scores At-a-Glance (5.00 = highest rating, 0.00 = lowest):

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)

The study advised that passengers should never drink unsealed water on while flying. The report suggested not washing your hands and to not drink the tea or coffee aboard a plane

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)