Aviation industry could cut climate impact by 20% in five years, study shows

Modifying air traffic control procedures and aircraft operations can reduce the industry's footprint, University of Bristol research shows

An Air France aircraft, operated with sustainable aviation fuel produced by TotalEnergies, is refuelled before its first flight from Nice to Paris in October. Reuters

The aviation industry can drastically reduce its environmental impact with only minimal changes to aircraft equipment and infrastructure, according to the findings of a new research paper.

Modifying air traffic control procedures and aircraft operations can reduce the industry's climate impact by as much as 20 per cent in the next five to 10 years, University of Bristol researchers found in a paper published in the journal Aerospace.

Non-CO2 emissions from aircraft account for more than two-thirds of aviation’s net climate impact, yet due to the focus on decarbonisation in policymaking — which is necessary to meet net zero targets — mitigation of these emissions is often overlooked, said lead author Kieran Tait.

"Flight route modifications in the form of climate optimal routing, to avoid climate-sensitive regions, and formation flight, in which two aircrafts fly one behind the other (separated by about 2km) could hold the key to drastically reducing aviation's climate impact," Mr Tait, who completed the review of the latest aviation emissions science, said.

Last year, airlines pledged to achieve net-zero carbon emissions from their operations by 2050, bringing the air transport industry in line with the objectives of the Paris Agreement to limit global warming to 1.5°C above pre-industrial levels. Airlines are facing pressure from environmental groups to lower their carbon footprint and to build back greener operations after the Covid-19 pandemic.

In October 2021, at the 77th Annual General Meeting of the International Air Transport Association in Boston, US, the industry lobby group outlined plans for achieving this target through a combination of eliminating emissions at the source (such as the use of SAF and improvements to air traffic navigation), offsetting and carbon capture technologies.

The research paper's findings echo Iata's net-zero plan that calls for improvements in aircraft operations and operational efficiency, with a particular focus on improved air traffic management.

There are two main contributors to aviation's non-CO2 climate impact – aircraft condensation trails (contrails) and emission of nitrogen oxides (NOx), the paper explains.

The warming effect of non-CO2 emissions strongly depends on the chemical and meteorological state of the atmosphere at the instant they are released.

Contrails account for 51 per cent of aviation’s total climate impact. Where the air is very cold and humid, the water vapour in the contrails condenses around particulates to form ice crystals which trap heat and have a net-warming effect.

Emissions of NOx react with chemicals in the atmosphere to generate ozone and reduce methane. However, the generation of ozone tends to outweigh the methane reduction, leading to a net warming effect.

“While climate optimal routing may require a longer flight, and therefore an additional one to two per cent fuel burn, avoiding climate-sensitive areas could actually reduce the overall climate impact of a flight by around 20 per cent," Mr Tait said.

“In formation flight, the follower aircraft flies in the wake of the leader aircraft, receiving an upwash which reduces the required lift and results in a five to eight per cent decrease in fuel burn. It also has the additional benefit of overlapping of aircraft exhaust plumes, and the accumulation of emissions contained within them."

The next step is to analyse global air traffic data to identify high-density airspace hotspots (such as along flight corridors), where implementing the formation flight concept would be best suited, Mr Tait said.

This paper gathers the latest evidence of the aviation industry’s climate impact and concludes, “this is how we can make a real and significant difference, right now”.

"The aviation industry has a lot to gain from taking these findings on board and making the small but crucial changes to air traffic control and aircraft operations that will have such a significant impact," said Steve Bullock, associate professor of aerospace engineering, who supervised Mr Tait’s research.