Every spring and summer, the headlines appear more familiar: Airlines are grounding flights because it’s simply too hot to fly. These declarations often come out of the toastiest U.S. cities, like Phoenix, which last year set a personal record of “most number of days over 110 degrees Fahrenheit.” Like humans on particularly scorching days, planes often can’t operate properly in extreme heat. In these cases, the aircraft is physically unable to take off because of the temperature.
It’s an awkward situation for airlines and their customers, who might not get why the perfect-seeming weather is stopping their trip. “You can see snow, you can see ice on the wings, you can see heavy rain or lightning, and you don't want to get in a plane when that's happening,” says Jennifer Griswold, an atmospheric scientist at the University of Hawai'i at Manoa. “But if it's just sunny and really bright out and there's not a cloud in the sky, it’s like, what’s wrong?” Meanwhile, flight operators are keenly aware of how quickly extreme heat can derail flight plans — and know that it’s going to become an even larger stumbling block in the future.
