As air transport becomes increasingly less glamorous, passengers find themselves grateful for even the smallest in-flight comforts. Beverage service is an amenity that frequent fliers can still depend on, and the arrival of the drinks cart signals the opportunity to enjoy a cold soda or a hot cup of tea. Caffeine lovers, however, often get their hopes up for a fresh, strong sip of coffee, and are inevitably disappointed by a mediocre brew. It’s not a mass hallucination; in-flight coffee really is underwhelming. The Kitchn investigated and found out this is for a number of reasons.

The usual culprit in a case of not-so-great coffee is the beans: low-quality beans naturally lead to a low-quality beverage. While airlines might conceivably want to cut costs by stocking up on the cheap stuff, coffee culture is such a force now that most flight providers wouldn’t dare. In fact, certain airlines proudly advertise the quality of their coffee sources. Clearly, the beans aren’t to blame.

Once the coffee beans have been ruled out, the next most obvious ingredient that could be at fault is the water—the very same water that, according to a 2012 EPA report, tested positive for coliform and other harmful bacteria in 12% of test cases from commercial airline water supplies. While that might be one reason to eschew in-flight coffee altogether, bland coffee probably isn’t caused solely by coliform bacteria.

Actually, there are likely other factors at play: humidity, noise, altitude, and air pressure. Just as a dry airplane cabin can cause food to taste bland, it can do the same to coffee, which falls victim to the same desensitization of a passenger’s taste buds to sweetness and saltiness, and to the the failure of about a third of them entirely. Odor receptors don’t function as well in flight either, and a normally aromatic coffee smells—and tastes—not much better than hot brown water. Even the noise of the turbines dampens passengers’ enjoyment of their coffee break, as the 85 decibel drone interrupts a brain’s ability to identity and taste flavor compounds.

All of this spells bad news for caffeine fiends—as long as it’s 10,000 feet in the air, that cup of coffee is going to taste pretty blah. As far as alternatives go, wine is no better (perhaps even worse). Delta Airlines sommelier Andrea Robinson notes, “subtlety is not well served at altitude.” However, there may be hope yet for an in-flight treat. Marion Nestle, NYU professor of nutrition and food studies, says ice cream should still taste fine, no matter how far off the ground you get. So get on it, airlines; my frequent flier miles and I will be waiting impatiently for our complimentary in-flight ice cream service.

[h/t The Kitchn]