Why do airliners have dark bellies?

John Schumacher from Succasunna, New Jersey asks, “Why is the bottom of an airliner painted dark?”

The answer is that not all of them are. And those airlines that choose to paint the bottom of the fuselage a dark color are probably doing so on the advice of their marketing folks. “There’s no safety or maintenance reason for painting the belly,” says Steve Lott, vice president of communications at the Air Transport Association in Washington, D.C., which represents 15 U.S. airlines. “It really boils down to the airline’s marketing or branding firm and what they come up with for the livery. A lot of times, the belly might be darker to highlight a lighter color on top.”

Some airlines tinker with color schemes more than others, Lott points out. American Airlines, for example, has kept the polished aluminum look for its carriers for years, while United is now changing its livery from a white top and royal blue belly to a white top and light gray belly. “A lot of it has to do with the designer’s look, but you want to keep the aircraft consistent,” he says. No matter what color is used, the paint on the underside of the fuselage is standard airplane paint, nothing special.

To paint or not to paint, it doesn’t seem to make much difference weight-wise. A few years ago, Air Canada stripped the white fuselage paint off a single 767, in a test to see if it could realize savings in fuel costs by making the airplane lighter. Turned out the savings were not enough to offset the outcry from upset passengers, who hated the new look.