Airline passengers have enough to worry about with food that tastes like salted cardboard, pilots who might be violent felons, days-long flight delays, and the looming threat of your jet falling like Boeing’s stocks (or, even worse, falling like Boeing’s planes). So there’s no need to add lung cancer to the list of hazards passengers have to grapple with. Yet as CNN’s Jon Ostrower points out, airplane restrooms are equipped with “a tiny ashtray that pulls out from the wall” next to the door. Smoking is an obvious no-no on airplanes, so why does this feature even exist? 

The short answer is that people suck — specifically, they suck and blow smoke even when they aren’t supposed to. In fact, this happened in 2019. Per CBS affiliate WTKR, a Spirit Airlines passenger received a lifetime ban after drunkenly smoking a cigarette in his seat. And way back in the ancient days of 2018, a Southwest Airlines plane was forced to land after a passenger decided to light a mouth chimney in the bathroom, according to Business Insider. Hopefully, the smoker at least used the conveniently stashed ashtray. 

Bans and unplanned landings are the least of an airline’s worries, sadly. Keep in mind that smoking used to be permitted on planes. Air and Space magazine notes that in the 1930s, some luxury flights provided “complimentary in-flight cigarettes,” and the U.S. didn’t officially ban smoking on flights until 1996. So there’s a fairly clear picture of how bad things can get when people start puffing nicotine sticks in the sky. 

One of the problems that arose before the ban was that people used to toss cigarettes out of windows, posing a risk of forest fires. But the worst-case scenario happened in 1973 when a Varig Airlines flight crashed in Paris, killing 123 people. OZY writes that a passenger might have tossed a still-lit cigarette into the bathroom trash bin, causing a fire that doomed the flight. According to the New York Times, it was the second worst air disaster in France’s history at the time. The plane “skidded about 500 yards across rows of onions, lettuce and beets” and came to a stop about 200 yards from homes in “a heavily populated” suburb. The resulting fire was  so intense that it “melted away the left rear section” of the plane. When that kind of awfulness is possible, it’s better to be extra-safe — and have planes equipped with ashtrays — than be extremely sorry.