Why do we drink so much tomato juice on planes?

United Airlines know a thing or two about weaselly management-speak. Last year when a passenger was forcibly removed by police from an overbooked flight, bleeding and screaming, their spokesman initially called it as an “involuntary de-boarding situation”. CEO Oscar Munoz doubled down, referring to the removal as “re-accommodating the customers”.

This week the airline announced they were “streamlining” their onboard menu items on flights under four hours – their way of saying customers would be getting less food and fewer options. Muffins would replace hot breakfasts, wraps would replace full lunches, and tomato juice as a beverage option would be phased out.

Customers were quick to express their outrage, and today United U-turned on the tomato decision. So why is the beverage – which is not particularly popular under normal circumstances in America – drunk so much on planes?

There have been a number of scientific investigations trying to answer that question. In 2015, Robin Dando, a physiologist at Cornell, found that exposure to loud noises, like that of a jet engine, dulls sweet flavours but intensifies the umami taste present in tomato juice. Five years earlier, German airline Lufthansa commissioned research into the popularity of tomato juice when they realised they were serving 53,000 gallons a year.

Researchers from the Fraunhofer Society found people enjoyed it more on planes because our taste and smell receptors are less sensitive at altitude, which means people enjoy the freshness of the juice without the earthy, mulchy taste.

Those research-based accounts seem somewhat contradictory, though: can the taste of the drink be both enhanced and dulled? Even if they can, do ordinary passengers know that before they order the drink?

It’s more likely there is a psychological basis for the popularity. Choosing a drink on a flight is an unusual situation: you have to decide when the trolley comes to you whether you’re thirsty or not. The beverage is normally free – meaning you want to extract as much value as possible. Tomato juice hits an odd sweet spot: it’s the only drink on the trolly that feels healthy, extravagant and unusual – plus you’ve seen so many other people order it, it becomes a tradition, the same way you eat popcorn at the cinema or hotdogs at a baseball game.

There might be another reason too, which goes back to United “streamlining” the food options. With less free food available on flights, many people are hungry when the drink cart comes around but don’t want to pay for a meal. Tomato juice has a lots of fibre and high water content, and makes you feel full even when you’re not. It’s basically a cold soup; you could even call it a free meal.

So congratulations to United for realising their huge screw-up and reinstating it. Or, as a United spokesman put it, in the company’s inimitable style: “With all of our food offerings, we monitor customer feedback and what they would prefer and adjust accordingly.”