The next time you’re flying, you may want to think twice about requesting for hot beverages or even washing your hands in the plane’s washroom. Drinking water provided on airplanes may be dirtier than you think, according to results from the 2019 Airline Water Study.

Non-profit organisation DietDetective.com and Hunter College New York City Food Policy Center studied and scored the quality of water onboard 23 airlines in the United States — 11 major and 12 regional airlines — and ranked them. Airlines outside of the US were not included in the research.

Water stored in the airplane’s water tanks for flights generally have a couple of uses: to make hot coffee and tea in the galley, and in the lavatories. Now you know why there are signs in the loo warning you not to drink the water from the sink.

Each airline was given a score out of five, based on 10 criteria. This included fleet size, violations of Aircraft Drinking Water Rules (ADWR) implemented by the government in 2011, and positive E. coli and coliform water sample reports. The presence of coliform bacteria in drinking water indicates that disease-causing organisms could be in the water system.

Under the ADWR, airlines are required to clean water tanks on the aircraft anything from once to four times a year, depending on the number of tests they do to detect traces of coliform bacteria and E. coli.

The major airlines with the cleanest drinking water are Alaska Airlines and Allegiant Airlines, who are tied in first place, albeit with a score of just 3.3 out of 5. Hawaiian Airlines is the runner-up, earning 3.1 out of 5 points. Delta Airlines ranked fifth with a score of 1.6 out of 5, and United Airlines is seventh, earning 1.2 out of 5 points. In contrast, Piedmont Airlines, which claimed the top spot for regional airlines, prevailed with a score of 4.33.

JetBlue and Spirit Airlines fared the worst, tying at the bottom with a score of 1 out of 5. Almost all regional airlines in the study had poor scores and a large number of violations of the ADWR, except Piedmont Airlines. Republic Airways (which operates United Express, Delta Connection and American Eagle) came in last with a score of 0.44.

Researchers behind this study have provided these tips:
#1: Only drink water that comes from a sealed bottle.
#2: Avoid drinking tea or coffee on flights.
#3: When you go to the loo, use the hand sanitiser (or better yet, bring your own sanitiser), instead of washing your hands in the bathroom.

Major airlines:
1. Alaska Airlines: 3.3, Allegiant Air: 3.3
2. Hawaiian Airlines: 3.1
3. Frontier Airlines: 2.6
4. Southwest Airlines: 2.4
5. Delta Air Lines: 1.6
6. American Airlines: 1.5
7. United Airlines: 1.2
8. JetBlue: 1; Spirit Airlines: 1

Regional airlines:
1. Piedmont Airlines: 4.33
2. Sun Country Airlines: 2.78
3. Envoy Air: 2.11
4. GoJet Airlines: 2
5. Trans States Airlines: 1.78
6. Compass Airlines 1.22; PSA Airlines: 1.22
7. SkyWest Airlines 1.11
8. Endeavor Air: 0.78
9. Air Wisconsin Airlines: 0.68
10. ExpressJet Airlines: 0.56
11. Republic Airways: 0.44

Photos: Unsplash