Warning over drinking water on planes following major new study

A new study suggests that the drinking water handed out on some of America’s top airlines may not be as safe as it seems.

While flying among the clouds can be exhilarating, it often comes at the expensive of some major health setbacks, including dehydration.

According to the US National Academies of Sciences, Engineering, and Medicine, adequate daily fluid intake sits at around 3.7 litres of fluids each day for men, and 2.7 litres for women.

But if you’re on a long-haul flight, it can be extremely difficult to hit that goal.

Anamaría Teino, a doctor at Mehiläinen specialising in travel medicine, said you should try and drink 0.2 to 0.4 litres of water for every hour on a plane.

To meet this, experts at Abbott Nutrition recommend you take advantage of in-flight beverage services, choosing flavoured seltzers, herbal teas, or just plain water to rehydrate.

But, according to new research, guzzling these onboard drinks may not be so great after all.

The Centre for Food as Medicine and Longevity has been investigating water onboard major and regional airlines since 1 October 2022.

The study concluded on 30 September 2025, and saw the experts taking a whopping 35,674 water samples.

Over the three year period, the scientists examined 10 major and 11 regional airlines' water, grading each company a ‘Water Safety Score’.

The score was based on each airline’s water quality and included: ‘Maximum Contaminant Level violations for E. coli, indicator-positive rates, public notices, and disinfecting and flushing frequency’.

Advice has been issued about your on-board drinking habits (Getty Stock Image)

A rating of 3.5 or higher was considered safe, while many airline scores reflected ‘potentially unhealthy water’ onboard, as reported by People.

The study found that Airlines which made it into the Grade A category were Delta Airlines - which was awarded a perfect score of 5.00 - and Frontier Airlines [4.80].

Snatching third place was Alaska Airlines, which achieved a B Grade with a score of 3.85, according to Charles Platkin, director of the Centre for Food as Medicine and Longevity.

The expert has stated that while Delta, Frontier, and Alaska should be praised, almost all regional airlines need to improve onboard water safety.

The exception here is GoJet Airlines, which primarily operates commuter flights and connects smaller cities to major United Airlines hubs.

GoJet Airlines was given the same score as third-place Alaska Airlines [Grade B, 3.85].

The worst offender in the major airline study was American Airlines. It was awarded a D Grade with just 1.75 points.

Regionally, Mesa Airlines, headquartered in Phoenix, Arizona, had the lowest score of 1.35 [Grade F].

FOODbible has contacted American Airlines and Mesa Airlines for comment.

In light of the results, the Centre for Food as Medicine and Longevity has warned that you should refrain from drinking water that doesn't come from a sealed bottle while flying.

This also includes avoiding coffee and tea onboard and not washing your hands in airplane bathrooms.

Experts warn that you shouldn't drink coffee on flights (Getty Stock Image)

The Aerospace Medical Association (AsMA) also recommends ‘avoiding alcohol, tea, coffee and other drinks that contain caffeine when flying’.

This is because caffeine has a diuretic effect, possibly worsening dehydration in the low-humidity cabin environment.

The Center for Food as Medicine and Longevity also recommend packing sealed bottles onboard or using a refillable water bottle that was topped up in the airport.

If using an airplane's tap water is really necessary, then the experts said you should let the water run for 30 seconds so the stagnant water can be flushed out.