There's a small in-flight habit that quietly drives cabin crew crazy, and chances are you've done it: stacking your drink order. Water, coffee and a Diet Coke, all in one go — helpful for you, but a headache for the person pushing the trolley down a 300-seat cabin.

One US-based flight attendant, Jennifer L., explained the problem to Business Insider: service has to keep moving so the crew can reach every passenger. One drink per person per pass keeps the cart rolling. Multiple requests mean extra trips, juggling trays, and a delayed service for everyone sitting further back. Her suggestion is simple — order one drink, and once the crew has worked the whole cabin, they'll happily swing back for round two.

There's also a safety angle that most passengers never consider. A tray piled with three open beverages is awkward at the best of times. If you need to squeeze past to the lavatory, or worse, if the crew calls for an evacuation, a lap full of liquid is the last thing anyone needs.

Then there's the Diet Coke problem. It sounds like a joke, but it's pure physics: the fizz takes ages to settle, so the attendant has to pour, wait for the foam to die down, pour again, and wait once more. Multiply that by a full cabin of soda orders and you can see why it's the drink crew members quietly dread. If you're set on a fizzy drink, a can bought after security and carried onboard sidesteps the issue entirely.

None of this is about being scolded for wanting a coffee. It's about reading the room — or rather, the aisle. Alcohol in excess is the more obvious crew irritant, but small courtesies go a long way: one drink at a time, say please and thank you, and don't treat the galley like a bar with unlimited tabs. If you're genuinely thirsty for the long haul, stock up on bottled water airside before boarding, which solves both the bulk-order problem and the tiny cup issue in one move.

Is anyone going to be denied a second beverage? Unlikely — crew will almost always come back for you. But on a packed flight, the passengers who make the crew's job easier tend to be remembered for it, sometimes with a free snack or an extra splash in the glass. Order smart, sip happy.