When the drink cart rolls down the aisle on your next flight, what do you plan on asking for? According to a recent report, water quality on airlines is not something to be trifled with.

The 2019 Airline Water Study is a collaboration between dietdetective.com and Hunter College NYC Food Policy Center. The study ranks 23 airlines in two categories based on water health scores. On a zero–five scale, any score less than three is considered unhealthy. The study considers 10 factors, including fleet size, E. coli sample reports, coliform sample reports and airline cooperation.

Out of the 11 major airlines considered, Alaska Airlines (3.3), Allegiant Air (3.3) and Hawaiian Airlines (3.1) are the only ones with water considered relatively healthy. The rest of the major airlines, including Delta Air Lines, American Airlines and United Airlines, received unhealthy scores.

Among regional airlines, Piedmont Airlines, a subsidiary of American Airlines, is the only one to receive a healthy score (4.33).

Unhealthy drinking water on aircraft violates the EPA’s Aircraft Drinking Water Rule, which outlines exactly what water is, and isn’t, considered fit for consumption on aircraft. Click here for a full rundown of the law passed in 2011.

Despite the violations, the 2019 study finds the EPA rarely holds airlines accountable for violations to the rule. The rule is also less strict for airline water than it is for standard drinking water. The latter requires more extensive testing for different microorganisms.

The authors of the study recommend not drinking water on board unless it is clearly from a sealed bottle, not drinking coffee or tea and not washing hands in the bathroom. Instead, use hand sanitizer.

Read the entire study online. Do you drink coffee or tea when you fly? Does this report change the way you view airline water? Will you change your habits? Tell us. Email us at [email protected]. Please include your full name and location.