Travelers are accustomed to delays from thunderstorms, snow, or wind, but a clear, scorching day can be just as disruptive. When temperatures soar, the air thins, making it harder for aircraft to generate the lift and thrust needed for a safe departure. Airlines may then have to reduce the plane's load by bumping passengers, trimming cargo, or carrying less fuel.
This phenomenon is well-documented at airports in desert regions, from the U.S. Southwest to the Middle East. Yet even moderate heat can pose challenges at high-altitude airports or those with short runways. With climate change driving more frequent and intense heat waves, researchers say such disruptions are likely to become more common.
A recent incident in Las Vegas highlighted the issue. On July 24, American Airlines asked for volunteers to give up their seats on a flight from Harry Reid International Airport after temperatures hit 114°F (47°C). The carrier described weight reduction as a standard practice in hot-weather destinations to ensure safe takeoffs.
The physics are straightforward: hot air is less dense than cool air, reducing the lift generated by wings and the thrust from engines, explained Ross Aimer, a retired United Airlines captain and CEO of Aero Consulting Experts. “There is a science behind all this,” he said. “You can’t deny the science of flight and what it takes for an airplane to operate.”
Aimer compared the effect to athletes competing at altitude, as seen during the World Cup in Mexico City, where thin air left players fatigued faster. “Just like human beings, jet engines require lots of cool, dense air to perform well,” he added.
Before each departure, pilots calculate whether the aircraft can safely take off, considering weight, elevation, temperature, and runway length, said Alan Price, a retired Delta Air Lines captain. Airports like Denver, already at 5,000 feet, face thinner air, so even modest heat can affect performance. Similarly, short-runway airports such as New York’s LaGuardia or Washington’s Reagan National are more prone to weight restrictions during heat waves.
If the math shows a problem, airlines may lighten the load, add a refueling stop, or wait for cooler temperatures. But there are limits. “At some point, the numbers just don’t make sense,” Aimer said. “You could roll down a runway as long as you want, and you still can’t take off.”
The Federal Aviation Administration sets no single maximum temperature for takeoffs; limits vary by aircraft type, weight, and airport altitude. A 2017 study from Columbia University and NASA projected that by midcentury, some airports could see weight restrictions on 10% to 30% of flights during the hottest part of the day if emissions continue to rise. A later study found that four European airports might have to shed the weight of 10 passengers per flight by 2065.
Data from the Associated Press show that Phoenix Sky Harbor International Airport has averaged 43 days per year since 2020 with temperatures at or above 110°F (43°C) — more than triple the mid-century average. Las Vegas has seen about 18 such days annually since 2020, double the rate from the 1940s through 1960s. Palm Springs International Airport recorded 55 days per year this decade, an 83% jump from the 2000s.
While airlines have long managed hot-weather operations, the increasing frequency of extreme heat is raising concerns. As climate change accelerates, passengers may face more last-minute weight-related delays, especially at vulnerable airports. For now, safety remains the priority, but the industry may need to adapt to a hotter future.
