The UK’s University of Oxford has shared the findings of a new study, which states that global aviation emissions could be reduced by 50-75% by applying three strategies to boost efficiency: flying only the most fuel-efficient aircraft, switching to all-economy cabin layouts, and increasing passenger loads.
The authors of the study believe that a reduction of approximately 11% in global aviation emissions is achievable immediately if airlines operate the most efficient aircraft in their fleets more strategically on their existing route networks.
The researchers involved in the report, titled ‘Large carbon dioxide emissions avoidance potential in improved commercial air transport efficiency’ analysed more than 27 million commercial flights operated in 2023, covering 26,000 city pairs and nearly 3.5 billion passengers.
The researchers claim the analysis revealed “enormous variability” in emissions efficiency, with some routes producing nearly 900 grams of CO₂ per kilometre for each paying passenger – almost 30-times higher than the most efficient routes, at around 30 grams of CO₂ per kilometre.
The study was based on data from Airline Data, the International Civil Aviation Organization (ICAO), and the International Air Transport Association (IATA). The researchers say the data showed that the regions with the most inefficient flights were Africa, Oceania, the Middle East, Central Asia, and North America. The regions with the most efficient flights were Brazil, India, and Southeast Asia.
“Our results clearly show that efficiency-focused policy could swiftly reduce aviation emissions by more than half, without reducing flight numbers or waiting for future fuels. These are tools that we can use right now,” said report co-author Dr Milan Klöwer, from the University of Oxford’s Department of Physics.
The data analysed by the team showed that globally, average aviation emissions from passenger flights were 84.4 grams of CO₂ per kilometre for each paying passenger in 2023. The research team believe they identified three means of reduce this figure: operating only the most fuel-efficient aircraft, removing premium-class seating to carry more passengers, and raising passenger loads to 95%.
Focusing on the aircraft models used on flights, the researchers believe this factor can make a “significant difference”, with emissions ranging from 60–360 gram CO₂ per kilometre for each passenger. According to the analysis, replacing all aircraft with the most efficient models – identified as the Boeing 787-9 (long-haul) and the Airbus A321neo (short and medium-haul) – would result in claimed fuel savings of 25% to 28%.
Report co-author Dr Milan Klöwer, also from the Department of Physics, said that: “While it is economically and practically unfeasible to replace all older aircraft in the short term, this analysis shows the potential more efficient aircraft have in comparison to other efficiency gains. Realistically, this would be a long-term transition – one that could be promoted by policies that reward efficiency, so that the most efficient aircraft are favoured whenever replacement decisions are made.”
Seating configurations also matter, say the authors, since business and first-class seats are up to 5-times more CO₂-intense than economy class seats. The researchers found that increasing passenger numbers to the maximum seating configuration for the most efficient aircraft would further reduce emissions by 22% to 57%.
In 2023, aircraft passenger occupancy ranged from 20% to 100%, with an average of 79%. According to the analysis, increasing average occupancy to 95% would further reduce emissions by 16%.
The study estimates that, if these three measures were applied globally, emissions could be reduced by between 50% and 75% – although this full reduction would require systemic changes. The team claims that airlines could reduce emissions by around 11% by flying their most efficient aircraft on routes where they already operate.
Lead author of the report, Professor Stefan Gössling from Linnaeus University in Sweden said: “Efficiency-based policies have a great potential to curb aviation emissions, and can be in airlines’ own economic interest. But the reality is that many airlines continue to fly with old aircraft, low passenger occupancies, and growing proportions of premium-class seating.”
The researchers suggest that efficiency improvements could be promoted using policy tools and market-based measures, such as emissions ratings for airlines, adjusted landing fees based on aircraft performance, and carbon intensity caps – drawing parallels to standards used in sectors like household appliances and vehicles.
The report findings have been published in in Nature Communications Earth & Environment.
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