Can it be too hot for a plane to fly? What to know if you're flying from Phoenix

Air travelers in Phoenix might find their summer vacation plans disrupted by the very thing they are trying to escape in the hottest months of the year: uncomfortable, 110-plus degree heat.

The searing Phoenix summers are when demand is high for travel from Phoenix, as residents seek cooler destinations for heat relief.

But extremely hot temperatures can make it harder and more dangerous for planes to fly. They're also a strain on the outdoor workers responsible for integral behind-the-scenes labor such as fueling the planes, guiding them to where they can park, loading and unloading luggage.

Most airlines' planes are certified to handle Phoenix's summer temperatures, and airlines and airports have made preparations to ensure that employees who work outdoors stay safe in the heat.

Can it be too hot for a plane to fly?

Most commercial jets are certified to operate in temperatures above 120 degrees, including some that can handle 130-degree heat, said David Ryan, an assistant professor at Embry-Riddle Aeronautical University's Prescott campus.

Phoenix Sky Harbor International Airport staff told The Arizona Republic in 2023 that aircraft performance data goes "up to and above" 122 degrees.

That's a change from when Phoenix would get too hot for airplanes to fly and the Federal Aviation Administration issued ground stops for Sky Harbor.

"I remember about 10 years ago, the temperatures in Phoenix got north of 120 (degrees)," Ryan said. "And the charts, the performance data for the aircraft went up to 120. All the airplanes had to divert to cooler airports until such time it cooled below 120. I remember several airplanes coming down to Tucson, where (the temperature) was 118."

Because of aircraft performance improvements in recent years, planes flew with few to no issues in summer 2023 despite a record-breaking streak of days above 110 degrees in Phoenix. When the FAA issued a ground stop at Sky Harbor last July, it was because of a computer glitch, not extreme heat.

The last time heat grounded airplanes in Phoenix was in June 2017, when American Airlines couldn't fly Bombardier CRJ jets used for regional flights because the planes were only certified to handle up to 118-degree temperatures, and highs approached 120 degrees. About 50 flights were canceled.

Is it hard for planes to take off in hot weather?

Still, performance improvements don't necessarily mean hot weather can't negatively affect a flight.

Heat can influence many factors that affect takeoff, such as wind direction and speed, barometric pressure, runway conditions, whether air conditioning is on or off and the aircraft’s weight at takeoff, Kristi Tucker, a spokeswoman for aircraft manufacturer Airbus, told The Republic last year.

How does heat affect takeoff?

Because hot air is less dense than cold air, it provides less lift for airplanes, Sky Harbor spokesman John Trierweiler said.

That means an airplane needs to operate at a higher speed and use a longer runway to create the lift it needs to take off, he said.

When a pilot needs more runway than Sky Harbor's Center Runway can provide in the summer heat, airport staff will allow the plane to use the North Runway instead, Trierweiler said. The North Runway, primarily used by arriving planes, measures 11,489 feet long, according to Sky Harbor's website. It's nearly 1,200 feet longer than the Center Runway.

Pilots must ensure their aircraft's takeoff distance fits within the runway length and allows enough of a buffer to continue takeoff or stop the aircraft in that runway length so they can operate safely, Ryan said.

Emphasizing airport worker safety in hot weather

Airports and airlines also must plan for the safety of employees who work outdoors.

Last year, workers filed a complaint with the Arizona Division of Occupational Safety and Health alleging that Prospect Airport Services, a contractor at Sky Harbor Airport, failed to protect them from extreme heat hazards. This included restricting workers from carrying water in certain locations and on certain assignments.

Sky Harbor said at the time that it works with contractors to ensure employees have access to water; Prospect did not respond to requests for comment from The Republic.

This year, Sky Harbor airport staff provided heat safety information to outdoor workers months before the start of the heat season. The guidance included tips such as where to find water stations and wearing sunscreen and wide-brimmed hats. They also shared information about handling heat-related emergencies, like knowing where automatic external defibrillators and first aid kits are and how to report heat-related issues.

"The well-being of our employees and those of our tenants is of the utmost importance to us year-round, but especially during the summer with the increased temperatures," Trierweiler said. "We hope that the information we have provided to outdoor workers informs them of the resources available."

Southwest Airlines' heat safety program in Phoenix and other cities with extreme heat includes encouraging outdoor employees to take frequent indoor breaks and drink plenty of cold drinks and training employees to watch for signs of heat-related illnesses.

An airline spokesperson said most of Southwest's policies surpass the requirements of Phoenix's heat safety ordinance, adding the airline appreciates "the thoughtful approach to keeping safety top of mind for everyone who works outdoors."

Phoenix-Mesa Gateway Airport's safety plans for the summer heat focus on providing regular breaks, hydration and cooling towels, airport spokesman Ryan Smith said.

Last summer, the east Mesa airport "did great with the prolonged heat," Smith said. Allegiant Air, the Las Vegas-based ultra-low-cost carrier that operates almost all of the airport's flights, had no heat-related delays or cancellations.

Tips for flying during extreme heat

Ryan offers a simple tip that could help you avoid heat-related delays or cancellations: Book flights for the early morning or late evening when temperatures are lower.

The challenge is that extreme heat effects might not be known until a few days before they happen, Ryan said.

"Weather can be difficult to forecast on what day it’s going to happen," he said. "One day they might predict storms and storms form, or one-day storms occur that were not forecasted. For the most part, they’ve got a pretty good grip on at least a range of temperatures a week out. It's hard to determine farther out than that."

Michael Salerno is an award-winning journalist who’s covered travel and tourism since 2014. His work as The Arizona Republic’s consumer travel reporter aims to help readers navigate the stresses of traveling and get the best value for their money on their vacations. He can be reached at Michael.Salerno@gannett.com. Follow him on X, formerly Twitter: @salerno_phx.

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This article originally appeared on Arizona Republic: How hot is too hot to fly? How extreme heat affects airplanes