Delta reveals the most important rule for ordering a cocktail on your next flight

With long lines and cramped seats, flying these days can be quite a stressful activity.

Which is why many of us prefer to have a cocktail while on board the flight.

Fortunately, most US airlines offer a wide range of liquor in both their premium and economy cabins.

But not all cocktails are created equal. Even though complex boutique cocktails are all the rage these days, they aren't necessarily the best choice for an in-flight drink.

According to Brian Berry, Delta Air Lines' director of on-board services, the key to a great in-flight cocktail is simplicity.

"We suggest a limit of no more than three ingredients per drink," Berry told Business Insider in an interview. "Usually two mixers and one liquor."

Why is that?

Cabin crew, especially in economy, have to serve a large amount of passengers in a small amount of time and with limited space from which to serve them. As a result, boutique cocktails with their exotic ingredients and complex mixing procedures simply don't work in most situations on a plane.

Berry says that cocktails with any more than three ingredients have a tendency to be less consistent in their quality and slow down service.

But that doesn't mean we will all be relegated to a mundane whiskey and coke or a vodka tonic the next time we fly.

Delta, along with numerous other airlines, work with chefs and liquor distilleries to come up with signature cocktails that reflect local and seasonal tastes.

So there's that to look forward to.