Why Does Warmer Air Make It More Difficult for Planes to Take Off?

climate change/airlines
An Aegean Airlines Airbus A320 aircraft is seen during takeoff as it departs from Athens International Airport, Aug. 26, 2020. Nicolas Economou/NurPhoto/Getty Images

As climate change has shown its effects over the last few decades, average temperatures have risen all over the world. Many industries are attempting both to mitigate the effects of rising temperatures and also adapt to the changes that have already occurred. One such industry is commercial air travel.

Studies published in February 2020 by the journal Climatic Change and in December 2021 by Cambridge University Press show that warming air has actually made it more difficult for airplanes to take off over time.


Researchers gathered climate data and takeoff telemetry from 10 Greek airports, with some of the data stretching all the way back to 1955. Two vehicles were used for research: a short-range propeller driven plane known as the De Havilland Q400 and the Airbus A320 jet airliner.

How Do Higher Temperatures Affect Air Travel?

Overall, the data showed that as the temperature increased, air density decreased, causing takeoff speeds to slow down. Over time, this has had a clear effect on air travel. For the Q400 turboprop aircraft at Chios airport, the researchers charted that the average takeoff distance is 328 feet (100 meters) longer now than it was in 1974. This can present real problems for terminals that use shorter runways.

Guy Gratton, associate professor of aviation and the environment at England's Cranfield University and one of the authors of the 2020 study, asserts that many air traffic controllers may not have been aware of this effect. "I don't think that most are noticing the trends of climate change because their job is to plan each day's flights based upon the latest observations and forecasts. You really need to observe changes over at least a decade, as we did with our paper, before the average impacts become noticeable and significant."


Aside from lengthening runways, air travel experts have to drop vehicle weights to fight the air density problem. This likely means reducing the number of passengers and the amount of cargo allowed on an aircraft. The 2020 study found that at Chios, the maximum allowable takeoff mass was reduced from about 165,350 pounds (75,000 kilograms) in 1974, to 152,000 pounds (69,000 kilograms) in 2017. That's an 8 percent drop in carrying capacity over time. In the case of heatwaves, we've already seen airlines have to cancel tickets or ground flights entirely as a result of the hot air.

Although the study in Greece shows an obvious correlation between climate change and aircraft efficiency, we don't yet know how the effects will play out at every airport across the globe. A couple of runways in the study showed little change in their takeoffs over time. One even had a slight shortening in distance over the study period.

"Conditions are not changing uniformly around the world — as you can see even from within Greece in our paper, different locations are seeing different changes in temperature and wind, and also their runways are at different alignments and length, so the effects will not be uniform. Indeed, if you try hard enough, you'll find some places where climate change actually improves conditions. On average, of course, the effect is consistently of warming air, reducing wind strength, and thus increasing takeoff distances (or where runway lengths are limited, reducing payloads)."


Possible Effects of Rising Temperatures on Consumers

Gratton adds that the issue is more pronounced for larger aircraft, noting, "Changes in conditions tend to be more pronounced on jet airplanes — this is simply because they tend to need more runway, and thus are more affected by conditions that increase their takeoff distance." Large jets are exactly what the industry uses for mass transportation and shipping, so this presents an issue for everyone who needs those services.

Due to fuel costs and other economic factors, airline expenses have trended upward throughout the industry's history. This often leads to higher prices and less convenience for customers. It stands to reason that lower takeoff weights have already contributed to an increase in expense. After all, if an airline has to be pickier about how much weight it can carry, that eats into its profit potential.


What About Effects After Takeoff?

According to Gratton, the effects of climate change continue after takeoff as well. "At higher altitudes there are changes in wind and temperature that will make long distance flight slower, and on some routes will increase the frequency and severity of contacts with turbulence." This is backed up by data from the team's 2021 follow-up study. Slower speeds mean reduced efficiency and more fuel burned, which may also increase ticket cost.

This may give the industry further incentives to pursue more efficient engine and fuselage designs in the future. "In many places the impact will be of either reducing payloads (so fewer passengers, or less fuel — the latter reducing range) or just increased takeoff distances. We can also expect increased noise footprints, as airplanes make flatter or higher-powered climbouts. Of course, airliners are typically in service for around 20 years, so there's opportunity to deal with this in improved aircraft designs, which are also being constantly improved to reduce fuel burn, noise emissions and so on."