High temperature distorting the air on the runway in Washington DC (Picture: Paul J.Richards/AFP)
Rising temperatures are making it harder for planes to take off from runways, even at UK airports.
Flying, a major contributor to greenhouse gas emissions itself, is facing huge challenges from extreme heatwaves which appear to get longer and hotter each year.
Millions of people flew out of UK airports last year, but as searing weather systems become more frequent, there are fears that airlines could be forced to leave passengers on the ground.
So how hot does it have to get to stop planes taking off? And what is the aviation industry doing to keep them in the sky?
Why planes struggle in extreme heat
Denis Bilyarski, a manager of sustainable aviation at consultancy firm ICF, explains that heat is a concern for airlines because it reduces the wing lift on planes.
This is a problem for jets because they are already very heavy.
Denis told Metro.co.uk that while reduced wing lift is ‘not a safety concern per se’, it does impact the number of passengers and overall load capacity at relatively short notice – which can lead to delays or cancellations.
It comes after new research from ten Greek airports revealed how high temperatures and slow headwinds can reduce a plane’s maximum takeoff weight by as much as the weight of a passenger and their luggage.
Paul Williams, a professor of atmospheric science at the University of Reading, studied the airports to see how hot summer weather and other factors such as short runways impact planes.
A plane landing in Phoenix, Arizona, where extreme heatwaves are common each year (Picture: Brandon Bell/Getty Images)
What Prof Williams and his team found is that extreme heat means planes have less air to give them the necessary lift from the tarmac into the air.
‘In some really extreme conditions that can become impossible altogether,’ Prof Williams told CNN.
As the air warms, it expands so the number of molecules available to push the plane up is reduced, the professor explained. With every 3°C of rising temperature, jets get 1% less lift.
With global warming, Prof Williams said scientists are seeing ‘global stilting’ of beneficial headwind slowing down by 2.3 knots per decade.
And coupled with rising temperatures of 1.35°C each decade since the 1970s, according to his studies, the future of flying could soon look very different.
How hot does it have to get for planes to be grounded?
The maximum operational temperature for commercial flights is believed to be around 50°C.
Commercial aircraft can function up to this temperature at ground level, according to the US National Institute of Health.
In 2017, dozens of flights were cancelled at Phoenix Sky Harbor Airport in the US, when the mercury hit 48.8°C.
When the weather gets cold, common commercial planes can sustain temperatures as low as -55°C on the ground, and up to -80°C in the air.
Heat-related take-off issues are most common at airports at high altitudes, where the air in the atmosphere is already thinner. Combine this with short runways, and planes have little room to accelerate enough to lift off the ground.
Major UK airports have been affected by rising temperatures. One such incident took place at London’s City Airport during a heatwave in 2018.
How altitude affects planes
Although UK airports might not be the first affected by rising global temperatures, flights to holiday hotspots at higher altitude could become impossible in the future.
Airports at high altitude have naturally thin air and often short runways, giving jets less room to accelerate.
A plane is said to require 6,500ft of runway at 20°C, and 8,200ft at 40°C.
Heathrow Airport’s altitude pales in comparison to the likes of Daocheng Yading Airport in China, or El Alto International Airport in Bolivia.
Heathrow – the UK’s busiest airport – sits at just 83ft, while Daocheng is located at 14,472ft and El Alto at 13,323ft.
Will your flight get grounded because of heat?
If you’re flying across Europe in winter, the answer is: probably not.
But if you’re jet-setting at the height of summer, your flight could be axed.
This is what happened at City Airport in 2018 when aviation officials were forced to suspend flights after extreme temperatures caused issues with the runways.
The second smallest airport in London has a runway of just under 5,000ft, while Heathrow’s – the longest runway in the UK – is just under 13,000ft.
Flights have already been cancelled in the past because of heat (Picture: Carlos Garcia Rawlins/Reuters)
Sustainable aviation consultant Denis Bilyarski said scheduling more flights at cooler times of day – early morning and in the evening – could help to avoid some of the issues caused by extreme heatwaves.
However, the margin for doing this in busy travel periods is limited, he added.
Denis continued: ‘Heat is a concern for ground staff working around the aircraft and potentially for crews, especially if air conditioning is unavailable or inadequate.
‘Any increased energy demand for cooling both aircraft and facilities that is not met by additional renewable capacity will lead to increased emissions, further contributing to the underlying problem.’
What is the industry doing in response?
The multi-billion pound aviation industry has been researching the impact of climate change and working on solutions for years.
As Denis suggested, planes might be forced to depart at cooler times of day, along with the introduction of lighter aircraft.
These are more likely solutions for the industry than building longer runways at airports worst affected by extreme heat.
Professor Williams believes ‘there are lots of solutions on the table.’
Dozens of flights were cancelled in Phoenix, Arizona, in 2019 when temperatures climbed to 49°C (Picture: Brandon Bell/Getty Images)
He said: ‘One would be to schedule departures away from the hottest part of the day, with more early morning and late evening departures, which is a tactic already used in hot areas like the Middle East.’
Boeing already has a ‘hot and high’ option for some aircraft operated by airlines that service airports impacted by high temperatures.
But the good news is, it’s unlikely you will be kicked off your flight anytime soon.
Prof Williams added: ‘People being bumped off aircraft because it’s too hot is rare and will remain rare. Most planes are never at their maximum takeoff weight, so this will happen in marginal cases – mostly airports with short runways, at high altitude, and in the summer.’
Denis warned that the industry needs to be careful with its ‘immediate response’ to worsening heatwaves.
He said: ‘It’s important that the aviation industry accelerates its drive to decarbonize all aspects of flying – for example through the increased production and uptake of Sustainable Aviation Fuels (SAF) – and avoid these efforts being outpaced by the impacts of a changing climate.’
Get in touch with our news team by emailing us at webnews@metro.co.uk.
For more stories like this, check our news page.