Extreme heat can snarl flights even without a cloud in the sky

The stifling heat that's enveloped large swaths of the country like a suffocating blanket has implications for travelers, too.

That's because extreme heat can affect flights.

“The weight at which you can operate (max gross takeoff weight) decreases as the temperature goes up,” explained Kathleen Bangs, a former airline pilot and current spokesperson for FlightAware, which tracks flight status in real time. “The hotter and more humid the surrounding air is, the more aircraft components and airfoil performance degrade.” Airfoils are aerodynamic surfaces like wings that help aircraft fly.

There are maximum temperatures set for aircraft performance, but it doesn’t have to get that hot for flights to be canceled or delayed, among other disruptions.

Here’s what travelers should know.

Why can't airplanes fly in extreme heat?

“As either altitude or temperature increase, the performance of the engines and the aircraft deteriorate,” said Robert Mann, an independent airline industry analyst and former airline executive who is now president of R.W. Mann & Company. “Engines produce less power, wings produce less lift and the combination results in the reduced ability to carry revenue payload,” meaning passengers, baggage and cargo.

That can leave airlines with a choice: “Do I offload people?” Mann asked. “Do I wait until the temperature goes down for the rest of the day?” 

A third option, he said, is to “carry all the passengers and bags, but we won't load fuel to destination. We’ll have to stop somewhere between here and there to refuel.” 

He’s seen all three happen and personally been among those offloaded.

What is the hottest temperature a plane can fly in?

“It'll depend on the aircraft and on the distance you're expecting to fly it,” Mann said.

Another factor is elevation.

“When you combine high elevation and high temperatures, it becomes even more limiting,” Bangs said.

John Cox, a retired airline captain who runs the aviation consulting company Safety Operating Systems, previously recalled his experience one summer in Phoenix in a column for USA TODAY.

"The maximum temperature was 110 degrees Fahrenheit, and while we were on the ground, it exceeded that," he wrote. "Our dispatch office obtained performance information from Boeing for our specific flight, and that was sent to me, allowing us to depart after a slight delay."

How common are heat-related disruptions?

It’s hard to say how many flights are impacted by extreme heat because, as Bangs noted, those numbers get reported with other weather-related issues like thunderstorms. However, both she and Mann said heat-related disruptions are uncommon, particularly for large aircraft.

“Years ago jets couldn’t operate normally in extreme high heat surface temperatures, but with technological advances, that is not as much of an issue now, although crews still have to carefully monitor brakes to make sure they don’t overheat,” Bangs said.

Climate change, however, could change that.

“As global temperatures rise even a degree, it will make a difference,” Mann said. “At the margin, it may make enough of a difference that you have to consider either weight limiting the aircraft or changing the number of passengers you’re willing to load on that day.”

Can you get compensation for delays?Not always

Do flights get canceled due to extreme heat?

It's possible. When that happens, airlines will generally book travelers on the next flight with available seats.

Travelers who choose not to rebook are entitled to a refund for their canceled flight, according to Department of Transportation rules. That's true regardless of the reason or ticket type.

Mann encourages travelers to think ahead for any flight.

"I don't go to the airport without knowing what my alternative might be," he said. "Whether you're flying the airplane or whether you're a passenger on the airplane, you need to know what your alternatives are."