As you settle into your cramped seat for yet another transcontinental flight, the unmistakable sound of a beverage cart comes rumbling down the aisle. The cheery flight attendant arrives holding aloft tiny bottles of water and softly inquires, “Water?”

You muster a polite half-smile, quietly grateful for any measure of hydration to make the dry cabin air more tolerable. But before you accept that petite plastic cylinder of purported refreshment, you may want to reconsider. Because the truth is, the water offered on most major airlines is, to put it bluntly, utterly undrinkable.

“Never drink the water on an airplane unless you’re willing to risk becoming a human petri dish,” cautions Dr. Kendyll Gilkes, a food safety specialist at Kansas State University. “It’s an absolute cesspool of bacteria and contamination.”

Strong words, but ones supported by a shocking volume of evidence. According to a startling EPA study published in 2004, one in every eight planes failed the agency’s standards for safe drinking water. Bacterial counts in some water samples were up to 100 times above the permitted limit.

And it only seems to be getting worse. In 2012, the Federal Aviation Administration reported discovering not just high bacteria levels but actual insects in some aircraft water supplies. Yes, insects – like flesh-eating bacteria had suddenly become too boring for our drinking water.

The reasons behind this disturbing trend are varied and unsavory. For one, those innocuous-looking water tanks are only required to be cleaned at intervals stretching over years – a virtual eternity in bacterial time.

Add in erratic maintenance and the ever-present risk of contamination from the truck tanks used to supply the plane, and you have a microbial mélange festering in that compact aircraft vessel.

“Imagine taking your bathtub home from college and not cleaning it for four years,” posits Teri Morse, a former EPA scientist who led the study. “That’s basically what the airplane water tanks are like.”

I think we can all agree those are not images that mix well with drinking water.

Making matters worse, airplanes have ample opportunities for water to become tainted even after leaving the tank. Ancient rusty piping and stagnant liquid lurking in the galleys provide ideal habitats for all manner of harmful bugs like E. coli, salmonella, and whatever horrors usually slither under rocks.

If that’s not enough to make you dry heave into one of those tiny air-sickness bags, consider the 2019 case of a flight attendant actually being hospitalized and having part of her stomach removed after contracting a stomach-turning bacterial infection from drinking the plane’s water. So much for service with a smile.

And if you think you’re safe ordering coffee, tea or alcoholic beverages, all of which incorporate the plane’s sketchy aqua provisions, think again. Those beverages could just as easily have you worshipping the compact airplane lavatory for the duration of the flight.

“People don’t realize that tea and coffee are just concentrated versions of the water you’re being served,” says Gilkes. “I never drink either one.”

Which raises the obvious question – if airplane water is so demonstrably terrifying, why isn’t there more being done by airlines to rectify the situation? As with most issues involving corporate profits, the reasons tend to be pedestrian and maddening.

According to insiders, replacement of the notoriously iffy water tanks is a costly, labor-intensive process – one which already cash-strapped airlines are loathe to frequently undertake, even in light of the well-established public health risks.

While some more conscientious carriers do enforce rigorous tank cleaning policies, the evidence suggests too many still view proper potable water sanitation as more of a luxury than a necessity.

“Until there are clear legal requirements for constant cleaning and upkeep, far too many airlines are content kicking that can of bacteria-ridden sewage down the runway as long as possible,” says Sara Nelson, president of the Association of Flight Attendants.

Graphic? Perhaps. But accurate? Tragically so. Just ask your average overworked flight attendant, who likely harbors horror stories galore from being on the front lines of the airplane water wars.

“You have no idea how many times I’ve had to scrub down a sickened lavatory after someone drank the water,” laments Hank Lorenzo, a veteran United flight attendant. “The utter pandemonium that can erupt when someone gets violently ill because they had the temerity to expect clean drinking water is positively medieval.”

It’s an all-too-common scenario that plays out with alarming frequency at airports and gates across the nation. Water quality experts confirm that a slew of illnesses typically attributed to that catch-all diagnosis of “traveler’s diarrhea” are often just good old contaminated water working its dark magic.

So, given the apparent dangers, what’s an intrepid but inevitably parched air traveler to do? While never drinking the plane’s water is obviously advisable, that’s not terribly practical for the longer hauls.

Recommendations from industry insiders vary:

Some advocate sticking with bottled water or requesting drinks made with bagged ice, which is generally cleaner than the onboard water supply. Many also swear by the relative safety of hard alcohol and soft drinks, whose chemistry renders them less prone to bacterial growth.

And then there are the true paranoids who simply resign themselves to dehydration rather than risk the infestation roulette of ingesting anything liquid from 30,000 feet.

Personally, as someone still traumatized from a bout of airsickness triggered by a suspiciously off-tasting cup of airplane coffee, I opt for canned and bottled beverages only. Call me pathologically risk-averse, but the convenience of imbibing the free water simply isn’t worth spending the rest of my flight plastered to the toilet like an extra from Slumdog Millionaire.

Of course, we’d be remiss not to mention the collateral environmental cost of all those bottles and cans constantly being ingested to avoid bacteria-laden drinking water. The impact on landfills and recycling centers is Sisyphean, which is especially galling since the obvious solution involves simply properly sanitizing the existing water tanks and lines.

That such a basic health and safety consideration remains an afterthought for too many carriers is unconscionable – indicating either a shocking lack of competence or disregard for basic human decency. Either way, it seems a fitting metaphor for the broader shortcomings and injustices that plague the increasingly inhumane experience that is modern air travel.

So remember – next time that cheerful flight attendant offers you a glass of refreshing water during your cross-country aerial voyage, don’t feel bad about politely demurring. No matter how dire your thirst or how courteous the service, the toxic reality is that water simply isn’t fit to drink at 30,000 feet.

At least not until the airlines get their sanitation acts together and join the rest of us here in the 21st century. Until then, we’ll all just have to make do sipping warm sodas and praying for deliverance from the increasingly Stygian horrors of air travel.