Why Is It So Hard to Get a Good Cup of Airplane Coffee?

Just as airplanes need jet fuel to get them from airport to airport, air travelers rely on coffee to get them from gate to gate — and yet if there's a single aspect of in-flight service that has consistently earned a worse reputation throughout the decades than the meal, it's the insipid airline cuppa joe. Watery, tasteless and often tepid, the airline coffee we've come to know and loathe has gotten an even worse rap these days, with questions about the cleanliness of the water and tell-alls claiming that the crew doesn't go near the stuff.

Fortunately, experts say that the humble airline bean juice doesn't deserve quite the bad rap that it gets. That said, there's room for improvement — lots of it.

Why Is Airplane Coffee So Bad?

Brewing a decent cup of coffee on an airplane presents a lot of challenges in addition to the weight and space restrictions: you're just not going to get as wide a variety of blends or brews as you'd have on hand at your local Starbucks; the lesser quality of the beans and the water; and then there's the science, which seems to stack the deck against caffeinating yourself in style.

Let's start with bad news: Making coffee at 39,000 feet in the air is simply a different scientific undertaking than on the ground. If you'll refer back to your 7th-grade science textbooks, you'll remember that the boiling point of water is dependent upon two factors: temperature and pressure. At sea level, or one atmosphere, water boils at 212 degree Fahrenheit. As the altitude increases, the pressure decreases, and so does the temperature required to boil water (by about a single degree per 500 feet).

Luckily for passengers, airlines keep their cabins pressurized so that everyone survives the flight, typically at between the equivalent of 6,000 and 8,000 feet by the time an airliner reaches cruising altitude. At those pressures, water's boiling point is between 198 and 202 degrees Fahrenheit. The problem is that even though water more quickly transforms into vapor (the definition of boiling), it simply isn't as hot as it would be at sea level, which means that, in coffee terms, there's less "cooking" of the coffee beans being accomplished.

"The coffee tastes like hot water, and lighter-roasted and medium-roasted coffees require hotter water to get good flavor," said Vajra Rich, owner of Boxcar Coffee Roasters in Denver, where the boiling point is about 203 degrees. "You just can't taste it anymore. It's just not strong enough."

Then there are the dulled senses — especially smell. As any coffee aficionado knows, the true glory of a great cup of java is in its scent, and human noses just don't function as well in the dry, recycled-air cooler that is an airplane cabin.

"A good cup of speciality coffee can actually have several hundred more volatile compounds coming off it than even a fine wine, hence one might think aroma is even more important for coffee and more adversely impacted than wine in the air," Charles Spence, an experimental psychology professor at Oxford University who's conducted widely publicized research on human palates in airplanes, said in an email. "Nice coffee is special in that the orthonasal sniff when we breathe in is often so much better than the retronasal taste/flavor experience when we swallow. This makes coffee special."

Then there's the water. The water tanks of an airplane are typically filled using municipal water from whatever town or city the departure airport's in, meaning that the quality of the source water can vary wildly from place to place, trip to trip, leg to leg. What's more, the cleanliness of the tanks has come into question; in 2012, NBC reported that the Environmental Protection Agency found at least one positive test for coliform bacteria in 12 percent of commercial planes in the US, a sign that there could be harmful bacteria in an airplane's water system. And various insider accounts on sites like Reddit have painted even more stomach-churning pictures, including water-tank trucks parked right next to latrine hoses, or flight attendants who claim they aren't even given cleaning supplies for the coffee machines. These tattletales, usually claiming to be airline pilots, attendants or employees, swear that they never touch airplane coffee.

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Why There's Hope for Airplane Coffee

Now the good news.

"Flight attendants like to make that sh*t up," said TPG contributor Carrie A. Trey, who works as an attendant on international flights for a major carrier. "We absolutely drink the coffee. In fact, when you have one crew coming in, one of the first things you do is put on a fresh pot of coffee for the pilots and crew. That's just standard practice."

And though everyone can agree that finding even one sample of coliform bacteria in an airplane water tank is cause for concern, the rates actually seem to be improving — at least somewhat. The 2012 rates were down from what the EPA found in 2004, when 15 percent of the planes it inspected had coliform. Still not great, obviously, but the EPA said it doesn't have any documented cases of passengers falling sick from the onboard drinking water. So even if the airplane water tastes like death, it probably isn't going to kill you. (Trey said that, in her experience, you're more likely to see sloppy water-handling practices on regional jets at smaller airports than on international or long-haul flights out of major hubs.)

As for all that science that's standing in the way of a good airplane coffee, there are things that can make it better. Using a dark roast, for example, makes a huge difference, Rich said.

"Darker-roasted coffee, like Starbucks, requires a little less heat, because, as the roast progresses the cellular structure of the coffee becomes more fragmented and brittle, and it's easier to wash those compounds out of those microscopic pockets and into your cup to drink it," he said. "So I would say on an airplane you could get a decent dark roast of coffee."

How Airlines Are Trying to Improve

The airlines know all about the science too, of course, and most American airlines have partnered up with well-known brands to develop brews that passengers already know and can enjoy even at high altitude. Delta and Alaska have linked up to serve Starbucks blends in the air, while American brews up Java City, United pours illy dark roast, and Southwest gives out Community Coffee. In the Northeast, New York-based JetBlue joined forces with Massachusetts-based Dunkin' Donuts to create a blend that would taste like the donut chain's familiar original brew in flight — "smooth, good amount of body and bright acidity without being bitter, with a nice clean finish," according to Ellen Rogers, Dunkin' Donuts senior manager of commercialization for coffee and beverages.

"We were able to figure out how much the coffee-to-water ratio was we would need to use, and though we had some limitations, we played around with the blend to find something that lived up to the same acidity that we look forward to," Rogers said. "We played with grain size — the finer it is, the more flavors — and came up with a blend of fine and coarse grinds and more Colombian coffee for acidity."

Dunkin' Donuts even made sure its coffee would be served alongside light cream from dairies it works with in the Northeast, part of what the company considers its signature experience. The final test was leaving the lab and flying from Boston with all the necessary equipment and, of course, tasting the new in-flight blend.

"We felt really comfortable with the profile we were looking for," Rogers said.

But there's still one aspect of a great cup of coffee no one seems to be able to crack, she admitted, and it's a big one: "You're not getting the aroma when it's brewed, and it's served on JetBlue with the lid, so you're not getting to get as much of the aromatics as you would with a regular mug of coffee. Aroma was a lower priority than flavor."

Right now, there's no solution, but Rich offered a temporary fix for coffee fiends who just need to make their caffeine fix as satisfyingly odoriferous as possible.

"You could bring a little extra powdered coffee that you like, ask the flight attendant for a cup of hot water, and make your own coffee," he said.