Why didn't Phoenix's historic heat wave ground more Sky Harbor flights? It's complicated

July’s enervating inferno failed to engulf Phoenix’s airplanes.

Despite a record streak of 110+ degree temperatures in the city and extreme heat, that years ago was high enough to ground airplanes, flights at Phoenix Sky Harbor International Airport operated normally all month.

“There have been no flight cancellations due to heat and we’ve seen very minimal impacts,” Sky Harbor spokeswoman Tamra Ingersoll said.

Extreme heat can affect an airplane's performance because hot air is less dense and generates less lift, making it harder for an aircraft to take off.

What’s changed since the scorching summers of 1990, 2013 and 2017, when the hottest temperatures kept planes from flying in Phoenix?

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Not much — summer in Phoenix still feels like walking through a fireball — except for one key difference.

Today’s aircraft manuals give pilots more information about how to fly in hot weather.

Were flights in Phoenix grounded because of extreme heat?

Yes, but not in 2023.

The first time flights at Sky Harbor were grounded because of extreme heat was on June 26, 1990, when Phoenix experienced its record high of 122 degrees.

It happened again in 2013 and 2017, when temperatures hit 119 degrees.

Looking back on the historic high of 1990, the Federal Aviation Administration issued a ground stop for Sky Harbor that day because of the extreme heat, Ingersoll said.

A ground stop is when planes cannot take off or land at a particular airport, according to the FAA.

The issue had nothing to do with the airport, Ingersoll said. Instead, it was in response to the airlines’ flight manuals, which explained how the aircraft would perform in hot temperatures.

“Because hot air is thinner, the performance of the airplane changes,” Ingersoll said. “However, the temperatures listed in those manuals didn’t go up to 122 degrees, so flights could not take off.”

What’s changed since those years?

The aircraft performance data pilots use has changed.

Airlines now have data that goes “up to and above” 122 degrees, according to Sky Harbor staff.

Still, other factors can determine whether a plane is able to take off, like wind direction and speed, barometric pressure, runway conditions, whether air conditioning is on or off and, most critically, the aircraft’s weight at takeoff, Airbus spokeswoman Kristi Tucker said.

Sky Harbor cites the materials in its runways and their varying lengths as keys to accommodating takeoffs and landings in the heat. Airport spokesman Eric Everts said the runways are made from 16-inch-thick steel-reinforced concrete.

Having runways of varying lengths supports airplanes’ performance in the heat, Ingersoll said.

“As it gets hotter, the heavier aircraft utilize the center and north runways, at 10,300 and 11,489 feet long respectively,” she said.

Expanding service: American Airlines is adding dozens of flights in Phoenix

Why was there a ground stop at the Phoenix airport on July 24?

The one time the FAA issued a ground stop for Sky Harbor in recent days was from 11:15 a.m. to around noon Monday, July 24.

But it wasn’t because it was too hot to fly.

FAA staff cited a telecommunications issue at its Albuquerque office for the stoppage, which delayed more than 200 flights by mid-afternoon July 24. FlightAware data showed 341 delayed flights that entire day, including 129 from Southwest and 106 from American.

Advisories from the FAA’s National Airspace System showed Southwest and American requested the ground stop.

Heat was only a minor factor. When The Arizona Republic asked Southwest Airlines why they requested a ground stop from the FAA, company spokeswoman Laura Swift said the airline needed to plan the sequencing of arriving flights so pilots wouldn’t need to wait long for a gate, citing the extreme heat.

The National Weather Service recorded a high of 116 degrees that day.

Unlike in 2013 and 2017, no planes were grounded because of heat when Phoenix experienced 119-degree temperatures on July 19, 20 and 25.

How does extreme heat affect air travelers?

Because weight affects an aircraft’s performance in high heat, airlines sometimes must reduce the amount of cargo and/or passengers to take off.

But American Airlines, which operates Sky Harbor’s largest flight capacity, told The Republic that its operating plan has accounted for “historically high temperatures at certain locations” to avoid weight restrictions that could affect passengers.

“Though we’ve had a very small number of diversions and delays related to high temperatures, the plan we have in place has allowed us to avoid significant impact,” American Airlines spokesman Curtis Blessing said. “We continue to monitor temperatures and ensure our team members who work outdoors are taken care of.”

Nationwide, Transportation Security Administration data showed heat waves aren’t keeping Americans from traveling.

TSA officers screened 2 million to 2.8 million passengers each day from July 1 to 27. All but one day (July 4) had higher numbers of screenings than the same day in 2022.

It won’t be known how busy July was at Sky Harbor until the end of August. The airport publishes each month’s passenger traffic data at the end of the following month.

Reach the reporter at Michael.Salerno@gannett.com. Follow him on Twitter @salerno_phx.

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This article originally appeared on Arizona Republic: Why Phoenix extreme heat wave didn't shut down Sky Harbor Airport