Extreme heat, often overlooked as a cause of flight disruptions, is increasingly challenging air travel. On the hottest days, thinner air can impede aircraft takeoff, prompting airlines to reduce passenger counts, cargo, or fuel, or to delay flights. This phenomenon is particularly noticeable in desert climates but can affect airports at higher elevations or with shorter runways.
On July 24, American Airlines offered compensation to passengers on a flight from Harry Reid International Airport in Las Vegas after temperatures reached 114 degrees Fahrenheit (47 degrees Celsius). According to the airline, reducing a plane's weight is a standard procedure in hot-weather destinations to ensure safe takeoff. The science behind this involves the physics of flight: hot air is less dense than cool air, which reduces the lift generated by an aircraft's wings and the thrust from its jet engines.
Ross Aimer, a retired United Airlines captain and CEO of Aero Consulting Experts, explained that like athletes at high altitudes, jet engines require dense, cool air to perform optimally. Pilots and airlines calculate critical factors such as aircraft weight, airport elevation, and outside temperature before each departure to determine safe takeoff parameters.
Airports at higher elevations, such as Denver, are already susceptible to thinner air, meaning less extreme heat can impact takeoff performance. Runway length also plays a role; shorter runways offer less distance for aircraft to build the necessary speed for takeoff in hot conditions. This can lead to takeoff restrictions or weight limits at airports like New York's LaGuardia and Washington's Reagan National during very hot weather.
When takeoff calculations indicate a safety issue, airlines may offload cargo, carry less fuel requiring a later refueling stop, wait for cooler temperatures, or ask passengers to volunteer for later flights. In some cases, Aimer noted, the aircraft's weight cannot be reduced enough for a safe departure, regardless of runway length.
The Federal Aviation Administration (FAA) does not set a universal maximum temperature for takeoff, as operating limits depend on the aircraft's specific model, weight, and the airport's altitude.
Research indicates that rising temperatures could exacerbate these issues. A 2017 study projected that by midcentury, some airports could face weight restrictions on 10% to 30% of their flights during the hottest parts of the day if greenhouse gas emissions continue to increase. Airports with short runways, high elevations, and hot climates are expected to be most affected.
Phoenix Sky Harbor International Airport has averaged 43 days per year with temperatures reaching at least 110 F (43 C) since 2020, a significant increase compared to previous decades. Similarly, Las Vegas has seen its annual average of such hot days more than double since the mid-20th century. Palm Springs International Airport recorded an average of 55 days this decade with temperatures reaching 110 F, an 83% increase from the 2000s.
Airlines have previously canceled flights due to extreme heat, including regional flights from Palm Springs in June 2016 and dozens of flights in Arizona in the summer of 2017 as temperatures neared 120 F. In July 2018, passengers were moved to later flights from Denver International Airport due to heat-related restrictions, and in July 2023, a Delta flight in Las Vegas was ultimately canceled after passengers spent hours on board amid extreme heat warnings and weight restrictions.
Airports can be particularly vulnerable to the urban heat island effect, where developed areas become hotter than surrounding regions. Factors such as limited shade, expansive heat-absorbing pavement, and the waste heat generated by aircraft, vehicles, and air conditioning systems contribute to these elevated temperatures, making airports exceptionally hot environments.