While airlines can have varying levels of services and amenities on flights, some things remain constant. The food is generally not great, the bathrooms are cramped, and seating anywhere other than first class can be uncomfortable.

You may have noticed one other fairly consistent feature, this one aesthetic in nature. Most airplane seats are blue. Carriers like Southwest, American Airlines, and United Airlines all feature the shade in their fleet. And there’s a good reason why. It’s the most practical color.

First, blue seats are among the easiest to keep clean—or at least the best way to give off the appearance of being clean. Blue allows smudges and stains to blend into the fabric in a way a white or darker seat would not.

Another reason is that many people associate the color blue with a sense of peace and well-being. Considering that anxiety about flying is common, it makes sense to have widespread use of a color that has a calming effect.

Airlines also use blue as part of a branding effort, with several major U.S. carriers opting for the color in logos because—along with red—it represents America. On a corporate level, it symbolizes a sense of trustworthiness, another positive when you’re allowing a pilot to carry you through the sky at speeds of up to 575 miles an hour.

You'll see other design choices on airlines—Virgin Atlantic, for example, has red seats—but chances are that blue will remain the most dominant color in the skies for the foreseeable future.

Mental Floss