Flight Challenges During Extreme Heat

Air travel passengers are typically aware that adverse weather conditions like thunderstorms, heavy snow, or strong winds can cause flight delays. However, extreme heat can also disrupt flights and travel plans.

On the hottest days, aircraft may struggle to take off due to thinner air. This reduction in air density can require airlines to lighten their loads by removing passengers, cargo, or carrying less fuel. This issue is prevalent at airports located in desert climates such as those in the U.S. Southwest and Middle East. High elevations or short runways can exacerbate challenges even under less extreme heat.

Human-caused climate change could make such disruptions more common.

Recent heat waves across the United States and Europe highlight how high temperatures can interfere with air travel. For example, on July 24, temperatures reached 114 degrees Fahrenheit (47 degrees Celsius) in Las Vegas, prompting American Airlines to offer compensation to customers voluntarily giving up their seats to reduce the plane’s weight for safe takeoff.

According to Ross Aimer, a retired United Airlines captain and CEO of Aero Consulting Experts, hot air is thinner than cool air. This phenomenon makes it challenging for a plane’s wings and jet engines to generate lift and thrust. He compared the effect of high temperatures on aircraft to athletes competing at high-altitude venues, which can lead to fatigue due to thinner air.

Airlines calculate several factors before a flight, including aircraft weight, airport elevation, and outside temperature, to ensure safe takeoff. At airports with higher elevations, such as Denver, which sits more than 5,000 feet above sea level, temperatures can quickly affect takeoff performance even when not extremely high.

Runway length also matters since airliners need enough space to build speed for takeoff when temperatures escalate. Longer runways are crucial when temperatures soar, a fact that makes shorter runways at airports like New York’s LaGuardia and Washington’s Reagan National more likely to face restrictions under hot conditions.

If calculations show an aircraft cannot safely take off as planned, airlines may take measures like reducing cargo, carrying less fuel for refueling stops, waiting for cooler temperatures, or asking passengers to volunteer for later flights. However, reducing weight may not always suffice for a safe takeoff.

The Federal Aviation Administration does not set a single maximum temperature for takeoff. Instead, operating limits depend on factors like aircraft model, weight, and airport altitude.

Research from Columbia University, NASA’s Goddard Institute for Space Studies, and others predicts some airports could face weight restrictions on 10 percent to 30 percent of flights during the hottest parts of the day by mid-century if greenhouse gas emissions continue rising. Airports with short runways, higher elevations, and hotter climates would be most affected.

Current climate prediction models suggest planes departing from four European airports might need to shed the weight equivalent of 10 passengers per flight by 2065. In places like Phoenix and Las Vegas, extreme heat affecting flights is becoming more frequent.

Phoenix Sky Harbor International Airport has recorded an average of 43 days each year since 2020 with temperatures reaching at least 110 F (43 C), according to weather station data analyzed by The Associated Press. At Harry Reid International Airport in Las Vegas, temperatures reached that threshold on average about 18 days annually between 2020 and 2025.

Palm Springs International Airport in Southern California experienced a significant increase in hot days, with an annual average of 55 days reaching 110 F — an 83 percent rise compared to the 2000s.

Airlines have adapted to these temperature challenges for years. American Airlines canceled several flights between Palm Springs and Phoenix during fierce heat in June 2016. In Phoenix, rising temperatures led the airline to cancel dozens of flights in 2017. In July 2018, airlines bumped passengers at Denver International Airport due to excessive heat.

Delta Air Lines also sought volunteers to step off a plane in Las Vegas during an excessive heat warning in July 2023 because of weight restrictions. That flight was eventually canceled after passengers spent hours on the aircraft.

Urban heat island effects can affect airports significantly. According to Jennifer Brady, a data scientist with Climate Central, these areas often contain little shade or green space, heat-absorbent pavements, and continuous activity. These factors contribute to making airports one of the hottest spots within a city.