Passenger planes have been approved to fly at higher temperatures in the US, following a request from American Airlines, which grounded dozens of flights last year due to extreme weather conditions.

Every aircraft has a maximum operating temperature, which is set by the manufacturer and approved by regulators. If the air temperature exceeds that limit then planes are not permitted to take off.

Such a scenario played out at Phoenix International Airport last year, resulting in dozens of cancellations, and more recently at Delhi’s Indira Gandhi International Airport, where delays were reported in June when the mercury nudged 45C (113F).

Keen to avoid a repeat of last summer, American Airlines – along with Mesa Airlines and SkyWest Airlines – asked Bombardier to increase the operating temperature of its CRJ jet, which had to be grounded during the heatwave.

American Eagle, the regional branch of American Airlines, uses the Bombardier CRJ Credit: ISTOCK

The CRJ had a maximum operating temperature of 47.7C (118F), which was a shade lower than the 48.3C (119F) recorded at the airport by the National Weather Service.

“After the summer of 2017, we approached Bombardier, along with Mesa and SkyWest, to see if it was possible to raise that limit to 50.6C (123F),” said Ross Feinstein, a spokesman for American Airlines.

“After multiple technical assessments with Bombardier, American, Mesa, SkyWest and the Federal Aviation Administration (FAA), approval was received to operate the CRJ at the higher limit.”

Embraer, one of Bombardier’s competitors, has also increased the temperature limit for some of its jets, a sign that the aviation industry is now preparing for a warmer climate.

“Rising temperatures have been an important design consideration for Embraer,” a spokesperson told Telegraph Travel.

Planes can struggle to generate enough lift when the mercury rises Credit: ISTOCK

In hot weather, planes can struggle to generate enough lift during take off because warm air is thinner than cool air. Some researchers warn that as the climate changes, cancellations due to high temperatures may become more common.

Here are five other ways climate change could impact air travel.

1. More turbulence



Bad news for nervous flyers. Passenger planes are likely to be buffeted by up to three times more turbulence in future decades, according to researchers at the University of Reading.

Scientists had already noticed that so-called clear-air turbulence (CAT) was on the rise, but the university is the first to come up with a comprehensive mathematical model predicting long-term global conditions. It estimates that by 2050 the rate of inflight injuries will have almost tripled in line with the increased volume of turbulence.

“Air turbulence is increasing across the globe, in all seasons and at multiple cruising altitudes,” said Paul Williams, Professor of Atmospheric Science at Reading, who led the study. “This problem is only going to worsen as the climate continues to change.”



The research team called for better forecasting systems so passengers can get seated and belted in time. They could soon have their wish. Boeing is preparing to test new laser technology that could allow pilots to detect clear-air turbulence up to 10 miles away.



2. Longer flights



Climate change is not just making turbulence more common; according to 2015 study, published in the journal Nature Climate Change, rising temperatures are also increasing flight times.



Scientists linked a small increase in return journey times of long-haul flights with an increase in the variation of the jet stream, the high altitude air that flows from west to east.



Just one minute’s extra flight time on every plane would mean jets spend approximately 300,000 hours longer per year in the air, they say. This would require roughly a billion additional gallons of jet fuel, thus releasing even more Co2 to the atmosphere.

“Upper level wind circulation patterns are the major factor in influencing flight times,” said Kris Karnauskas, associate scientist at Woods Hole Oceanographic Institution in Massachusetts. “Longer flight times mean increased fuel consumption by airliners. The consequent additional input of CO2 into the atmosphere can feed back and amplify emerging changes in atmospheric circulation.



“We already know that as you add CO2 to the atmosphere and the global mean temperature rises, the wind circulation changes as well – and in less obvious ways.”

Scientists claim climate change is already increasing flight times Credit: GETTY

3. More weight restrictions

Until new technology becomes available, there is little pilots can do to avoid lumps and bumps in the skies: clear air turbulence is not visible to the naked eye, isn’t detectable on radar and can’t be accurately forecasted.

However, according to Steve Allright, a British Airways pilot, one thing they can do is cruise at higher altitudes, though there are restrictions preventing them from doing so.



“Our endeavours to fly at an altitude that has been reported as smooth may be prevented by several constraints such another aircraft occupying that level, or the weight of the aircraft at that time,” he said.



If planes need to fly higher to avoid turbulence then they would need to be lighter, which means the weight of the aircraft – and possibly passengers' luggage, or even passengers themselves – could invite greater scrutiny.

4. Airport closures



The world's major airports were not built with climate change in mind – they simply needed to be far from big towns and tall mountains, so coastal areas and river deltas were often chosen. These low-lying sites, however, could now be vulnerable to rising sea levels.

Even a modest rise could affect hundreds of aviation hubs around the world. Some countries are taking steps to combat the risk. Norway, for example, has pledged to build all future runways at least 23 feet above sea level.

5. Longer runways



As outlined earlier, warmer temperatures mean planes have a tougher time taking off and during heatwaves airports with short runways are the first to face problems.

Back in 2013, 15 passengers were removed from a Swiss flight to Geneva after the plane was deemed too heavy to take off from London City Airport, whose single 4,900-foot runway is one of the smallest in the country.



Unless airports like London City lengthen their runways, this could become a more regular occurrence in the future.