The 2026 Airline Water Study by the Center for Food as Medicine and Longevity provided insights into the quality of onboard water served to passengers. The study encompassed 10 major and 11 regional airlines, spanning a three-year period ending in September 2025.

Water samples taken from aircraft water tanks were tested for E. coli and other bacterial species. Additionally, compliance with water safety regulations was assessed. About 2.7 percent of the more than 35,000 samples tested positive for coliform bacteria. Notably, one-third of CommuteAir’s samples exhibited positive results for coliform bacteria.

During the three-year study period, there were 32 violations for E. coli across the 21 carriers. The study authors noted that onboard water quality is influenced by the domestic or international source of the water and the equipment used to transfer it to the aircraft.

Each airline received a numerical score ranging from zero to five, accompanied by a corresponding letter grade. Four major airlines, namely Delta, Frontier, Alaska and Allegiant, received a grade of A or B. Spirit, JetBlue and American Airlines received the lowest scores, each earning a D grade. Nearly all regional airlines had poor water quality, with only GoJet earning a B grade. The remaining nine regional carriers earned C or D grades, while Mesa Airlines received an F.

The study’s authors advised passengers to never drink onboard water that is not from a sealed bottle. Additionally, they recommended avoiding onboard tea or coffee and using an alcohol-based hand sanitizer rather than washing their hands in an aircraft bathroom.