Extreme heat causes flight delays: aviation experts

Extreme heat is emerging as an increasingly important cause of flight disruptions, even on cloudless days when passengers would normally expect smooth departures. Aviation experts warn that soaring temperatures reduce aircraft performance, forcing airlines to limit passenger numbers, cargo or fuel loads, and, in some cases, delay or cancel flights.

The challenge is already familiar at airports in hot desert regions such as the U.S. Southwest and the Middle East, but researchers say climate change is making these problems more common elsewhere. Airports at higher elevations or with shorter runways are particularly vulnerable because aircraft already operate under more demanding conditions.

Las Vegas recently provided a clear example. On July 24, with temperatures reaching 47 degrees Celsius (114 Fahrenheit), American Airlines asked passengers to volunteer to give up their seats on a departing flight from Harry Reid International Airport.

Reducing an aircraft’s weight, the airline said, is a standard safety procedure used at hot-weather destinations whenever conditions require it.

The reason lies in basic physics. Hot air is less dense than cool air, making it harder for wings to generate lift and for jet engines to produce the thrust needed for takeoff. As temperatures rise, aircraft require more runway to accelerate safely before becoming airborne.

Retired United Airlines captain Ross Aimer said aircraft performance suffers much like athletes competing at high altitude. During this year’s FIFA World Cup, teams playing in Mexico City experienced thinner air that left players fatigued more quickly.

Before every departure, pilots calculate whether an aircraft can safely take off by considering several factors, including the plane’s weight, outside temperature, runway length and airport elevation.

Higher-altitude airports face additional challenges because the air is already thinner. Denver, for example, sits more than 1,500 meters above sea level, meaning temperatures do not need to climb as high before takeoff performance begins to suffer.

Runway length also plays a crucial role. Airports such as New York’s LaGuardia and Washington’s Reagan National have relatively short runways, leaving aircraft with less distance to reach takeoff speed during periods of extreme heat.

If calculations show a flight cannot depart safely, airlines may offload cargo, reduce fuel and schedule a refueling stop later, wait until cooler evening temperatures or ask passengers to volunteer for later flights. However, there are limits to these measures.

The U.S. Federal Aviation Administration does not impose a universal maximum operating temperature. Instead, takeoff limits depend on the aircraft model, its weight and the characteristics of each airport.

Researchers expect these restrictions to become more common as the climate warms.

A 2017 study by Columbia University, NASA’s Goddard Institute for Space Studies and the Logistics Management Institute projected that, by mid-century, between 10% and 30% of flights departing during the hottest part of the day at some airports could face weight restrictions if greenhouse gas emissions continue to rise.

Scientists say airports are especially susceptible because of the urban heat island effect. Vast expanses of asphalt, limited vegetation and continuous aircraft, vehicle and air-conditioning activity trap and generate heat, often making airports among the hottest places in a city.

As temperatures continue to rise, aviation experts expect extreme heat to become an increasingly frequent factor affecting flight schedules worldwide. MDT/AP