# This Is Why Flights Get Canceled When It’s Too Darn Hot Out

## Turns out, there’s a pretty legitimate (and scientific!) reason why higher temps in Arizona are keeping planes on the ground.

shutterstockWhen it comes to airport layovers, most of us are on the same page: shorter is much, much sweeter. But unfortunately for flyers in Phoenix, they are in for a pretty insane flight delay. (By the way, these photos prove just how crazy flight delays can get!) Airlines just canceled 40 flights out of Arizona’s capital city because it was too hot outside. Seriously!

Before you grab your pitchforks, there’s a very legitimate reason why. Wired reports that certain airliners can only operate at a max temperature of 118 degrees Fahrenheit, while bigger planes from Airbus and Boeing can handle up to 126-degree heat. With temperatures expected to hit 119 degrees in Phoenix this week, the carriers opted to keep their planes on the ground.

Their decision is pretty understandable once you get a physics lesson on how a plane flies. And the answer has everything to do with air density, Wired says.

Airplanes rely on pressure from air molecules to hold it up in the sky. As the air collides with the plane’s wing (or body, tail, etc.), it causes a difference in pressure between the bottom and the top of the wings; the pressure is lower above the wings, and higher below the wings. This creates a net force upward called the “lift.” The jet’s engine or propeller provides a thrust to increase the speed at which the plane hits the air molecules, generating enough “lift” to cause the plane to fly. As a general rule of thumb, the greater the air density, the greater the lift.

Now that we have the physics under our belts, we can circle back to those 100-degree-plus temps in Arizona. As the temperature outside rises, the movement of the air molecules increases, which causes the gas to expand and volume to increase. The air density decreases as a result, generating less lift. There’s the problem for Arizona: Local air density is currently too low for some of those planes to take off.

Still, Wired did offer stranded travelers one consolation for their canceled flights: “At least the airport has air conditioning.”

Can’t argue with that. In case you find yourself in Phoenix (or any place with blistering heat!) sometime soon, you might want to know how to make the most of your next airport layover—and we’ve got you covered.