Brooks Kraft via Getty Images Can you spot the ashtray?

Smoking on airplanes was officially banned on U.S. flights in and out of the country in 2000. But curiously enough, despite this smoking ban, new models of planes still come equipped with ashtrays in their bathrooms.

If you’ve ever wondered why that is, CNN’s aviation editor Jon Ostrower recently resurfaced the reason airplanes are required to have ashtrays. Ostrower, who says it’s one of the most-asked questions about airplanes he gets, says it all boils down to the Code of Federal Regulations.

“Regardless of whether smoking is allowed in any other part of the airplane, lavatories must have self-contained, removable ashtrays located conspicuously on or near the entry side of each lavatory door,” the regulation states.

As an FAA spokesperson told The Huffington Post via email, even though smoking isn’t allowed on planes, that doesn’t mean it stops determined smokers.

“Some people continue to try to smoke on airplanes,” the spokesperson said. “The ashtray provides a place to put a cigarette, other than the waste bin, or somewhere less desirable where the ashes might start a fire.”

And if you do get caught smoking on a plane, chances are you’ll get in big trouble once the flight has landed.

“The first thing we have to do is make sure they haven’t created a fire on board the aircraft, because a lot of times they’ll throw the cigarette down into the trash bin,” Tracy Sear, a then-US Airways flight attendant, told the New York Times in 2015. “Then at the same time we’re advising the passenger that they must comply and stop, and letting the cockpit know. Usually, the authorities will meet the flight when it lands.”

A few words of advice: just don’t do it.