A flight on Frontier Airlines between Los Angeles and Denver took a turn when a passenger pulled out her phone. The footage, posted on Twitter (X), shows a flight attendant filling empty water bottles from the plane's galley dispenser before handing them out. The passenger identified the flight as F9 2342 and captioned it with a few vomiting emojis — the internet's replies were predictably blunt, ranging from "well it is Frontier" to one Chinese-language comment asking whether this was a cost-cutting measure or a dark joke about passenger lifespans.

It's worth unpacking what actually happened here. Crew members pour water from the galley all the time; that's how a lot of inflight water gets served. The problem, as many travellers see it, is the bottle. People who carry an empty bottle through security and fill it before boarding are often doing so specifically to avoid aircraft tank water. Pouring tank water into the bottle removes the reason they brought it.

So how worried should you be about what's coming out of the plane's tap? Aircraft water is loaded at airports through servicing equipment, sits in onboard tanks and runs through the plane's plumbing — and its quality depends entirely on how well that system is maintained. It's supposed to be potable, and in the US the EPA's Aircraft Drinking Water Rule obliges airlines to sample it and run disinfection and flushing programmes. The author of the original piece has tracked this for years, including a water-quality report card in which Frontier scored a surprisingly strong 4.80 out of 5. Delta topped it at 5.00, while American (1.75) and JetBlue (1.80) brought up the rear among major carriers.

Still, even a good score doesn't convince everyone. The piece's author declines onboard coffee and won't use the lavatory tap to brush teeth on long-haul flights — a reasonable line for cautious fliers.

For context, this isn't the first time onboard service quirks have gone viral. An Emirates flight attendant was filmed pouring champagne from a glass back into a bottle in 2017, and in 2023 an American Airlines passenger flying San Diego to Charlotte reported watching a crew member return several cups of orange juice to the original carton. Unappetising to watch, even if the explanations (unused pours, surplus cups) are often more mundane than they look.

Why does this matter if you're planning a trip? If you're picky about water, you have easy options: carry a sealed bottle from landside, ask for a sealed canned or bottled drink if the airline offers one, or stick to drinks you know are made with boiled water like coffee and tea — assuming you trust the kettle. Budget carriers like Frontier keep fares low by trimming service everywhere, and cabin water handling is clearly part of what some passengers now scrutinise. Watching what goes into your cup isn't paranoia; it's just reading the fine print at 35,000 feet.

First reported by View from the Wing.