Why Do Flight Attendants Hate Serving This Drink to Passengers in Flight?

You may have heard the widely circulated rumor that ordering a certain drink while you're in flight can seriously delay beverage service for everyone else on board.

Sound familiar yet? Yes, the rumor implicates Diet Coke — and while that popular theory may be a little dramatic, it turns out there is indeed some science-based truth to the fact that diet sodas take longer to pour at altitude.

"Whenever a soda can is opened, the CO2 begins to go from a state of high pressure inside the soda to a state of low pressure in the open air," explains Bonham Forshage, a food scientist and head of product development at Eggwhites 24-7. "It does this by forming bubbles or fizz. At increased altitudes a higher differential between the soda and the air expedites this process meaning the soda both bubbles more and goes flat faster."

But what makes Diet Coke different from, say, regular Coke or a seltzer, ginger ale, or other carbonated beverage?

"The reason for the difference between the 'fizz' in Coke and Diet Coke is the same reason Diet Coke exists: It's the sugar. Sugar both increases viscosity and surface tension, allowing regular Coke to form larger bubbles that are weaker and pop faster. Diet Coke, on the other hand, forms smaller, stronger bubbles that pop much slower."

In the end, the total difference in serving time for each cup could be drawn out by a few seconds. If dozens of people on board are ordering Diet Coke, you could be adding a few minutes to the total drink-service time, and while that's really not the end of the world, it could be a game changer on a very short flight. And you can imagine that flight attendants, in an age of flight that prizes efficiency over anything else, don't really love it.