Can it be too hot for a plane to fly? How the Phoenix airport is handling record heat

When Delta Air Lines Flight 555 from Las Vegas was canceled before its intended July 17 departure to Atlanta, the inside of the plane was so hot that people fell ill.

Fox News field producer Krista Garvin recounted in a series of tweets that passengers were stuck on the plane for three hours while temperatures outside were around 111 degrees. Paramedics wheeled out at least three people who passed out from heat exhaustion.

Cities across the country, including Phoenix, are coping with extreme heat this summer. The heat can affect aircraft performance, such as by reducing the amount of weight the plane can safely carry. It can even be too hot for a plane to take off.

Despite this summer's record-breaking streak of 110+ degree days in Phoenix, airlines have reported few to no cancellations at Sky Harbor in recent days.

But the National Weather Service is forecasting 119-degree temperatures in metro Phoenix, how hot it was when Phoenix Sky Harbor International Airport most recently grounded flights because of heat in 2013 and 2017.

Air travelers should be aware of the potential hazards involved with flying in extreme heat.

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How hot is too hot for an airplane to fly?

It depends on the aircraft, the altitude and the total weight of the passengers and cargo, according to the Federal Aviation Administration.

"The majority of the airlines that serve Phoenix Sky Harbor have updated their airliner performance charts in recent years, with new data that goes up to and above the 122-degree range," airport spokesman Eric Everts said.

Most passengers who fly a major airline at Sky Harbor or with Allegiant Air at Phoenix-Mesa Gateway Airport will likely fly aboard a Boeing or Airbus jet.

While these large jets are capable of handling high temperatures, aircraft manufacturers are cautious to say there's no specific temperature where a type of airplane can or cannot take off. It depends on multiple factors such as wind direction and speed, barometric pressure, runway conditions and whether air conditioning is on or off, Airbus spokeswoman Kristi Tucker told The Arizona Republic.

"Airlines generate proprietary performance charts for the airports at which they operate, and there may be an upper limit to the outside temperatures for which their performance data ranges have been calculated," she said.

When was the last time heat grounded planes in Phoenix?

In June 2017, at least 50 regional American Airlines flights were canceled because of 119-degree temperatures. The regional flights, flown under the name American Eagle, used Bombardier CRJ aircraft that couldn't fly in temperatures above 118 degrees.

The 2017 cancellations were the most recent of three times in Sky Harbor's history when flights were grounded because of extreme heat. It first happened in 1990, when Phoenix hit its all-time high temperature of 122 degrees, and also happened in 2013, when temperatures reached 119 degrees.

Now, these near-record temperatures are returning. Phoenix observed a high of 119 degrees on Wednesday and the weather service forecasted the city would hit 119 again on Thursday and Friday.

Why is extreme heat bad for airplanes?

Air is less dense and generates less lift in extreme heat, making it harder for airplanes to take off, according to the FAA. In some cases, airlines must reduce the amount of cargo and/or passengers on the plane in order to take off in high heat conditions.

An airplane's weight at takeoff is the most important factor that affects its performance in extremely hot temperatures, Tucker said.

Ultimately, it's up to the airline and the flight crew to determine whether it's safe to fly based on the maximum temperatures and conditions, the FAA stated. The federal agency does not cancel flights.

How has the heat affected flights at Phoenix Sky Harbor Airport?

Data from the flight tracking website FlightAware showed few canceled flights at Sky Harbor in recent days, with 18 cancellations recorded from Monday, July 17, to Thursday, July 20. FlightAware's data does not specify why a flight was canceled.

In addition to airlines flying jets that can operate at high maximum temperatures, Sky Harbor's runways are able to accommodate takeoffs and landings in hot weather, Everts said. The runways are made of 16-inch-thick reinforced concrete, which can better handle extreme heat and the stress of heavy aircraft than asphalt.

"There is nothing that keeps the concrete from getting 'too hot.' It is just the design of the steel-reinforced concrete that enables it to withstand the extreme temperatures," Everts said.

How are airline workers handling the heat?

Some airline workers, including ground crews and baggage handlers, work outdoors.

That can be dangerous in extreme heat.

The New York Times published a story on how extreme heat affects workers, which included an account from a Phoenix airport worker. Some social media commenters singled out a passage in the story mentioning one of the airport's contractors, Prospect Airport Services, not allowing workers to bring water with them.

Sky Harbor tweeted in response to the concerns: "We work closely with our airport vendors and stakeholders to ensure their employees have access to water and receive proper information about staying hydrated."

A Southwest Airlines spokesman told The Republic that its workers are "trained and experienced in operating during heat conditions" and keep themselves and others safe by drinking water frequently, wearing protective clothing and looking out for other employees.

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

This article originally appeared on Arizona Republic: Extreme heat could affect whether your flight takes off. Here's how