Despite slackening growth in 2017-2018, demand for air transport is expected to remain strong in the future. Meanwhile, impressive efficiency improvements achieved since 2000 also show signs of slowing down.
Better aircraft utilisation is one of the reasons for improved energy efficiency. The average number of passengers, and the average weight of cargo per flight, have both increased, lowering energy use per useful service delivered. Another driver of efficiency improvement is fleet renewal. The fuel intensity of new commercial jet aircraft fell 1.3% per year on average from 1968 to 2014, roughly doubling their efficiency.
Aviation energy efficiency needs to improve by more than 3% per year to 2040 to be in line with global climate goals. Some of the policy infrastructure to achieve this is in place. Under the Paris Agreement and various other frameworks, certain countries have set up targets for efficiency improvements in domestic aviation. The International Civil Aviation Organization (ICAO) has put in place policies to improve aircraft efficiency and limit the growth in CO2 emissions of international flights.
A range of operational, technical and behavioural solutions, as well as further policy measures, will be required to cut emissions from 2025 onwards according to the IEA's Net Zero Emissions by 2050 Scenario. Near- to medium-term priorities include implementing fiscal and regulatory measures to promote efficiency; managing the investment risks for scaling up sustainable fuels; and developing alternatives to jet kerosene, such as battery-electric and hydrogen-powered aircraft.
Last updated Sep 27, 2022
Direct CO2 emissions from aviation in the Net Zero Scenario, 2000-2030
Global aviation emissions increased as countries emerged from Covid-19 lockdowns
In 2021 aviation accounted for over 2% of global energy-related CO2 emissions, having grown faster in recent decades than road, rail or shipping. As countries emerged from Covid-19 lockdowns, aviation emissions in 2021 reached around 720 Mt, regaining nearly one-third of the drop from 2019 levels seen in 2020. Many technical measures related to low-carbon fuels, improvements in aircraft and engines, operational optimisation and demand restraint solutions are needed to get on track with the Net Zero Emissions by 2050 Scenario – to curb growth in emissions and ultimately reduce them this decade.
Important recent policy developments that could help towards this end include the US Sustainable Aviation Fuel Grand Challenge announced in September, which includes funding to demonstrate fuel and aircraft technologies, and the proposed ReFuelEU Aviation regulation, which is currently under development and if adopted will set blending mandates for sustainable aviation fuels.
Activity growth outpaces fuel efficiency improvements, and progress has slowed
New aircraft are up to 20% more efficient than the models they replace, but this has been insufficient to keep up with growing activity. Between 2000 and 2010 fuel efficiency improved by 2.4% per annum, and by 1.9% from 2010 to 2019, demonstrating that additional incremental improvements are becoming more difficult. Meanwhile passenger demand grew at over 5% per year from 2000 to 2019, meaning that annual improvements are far below what is needed to align with the Net Zero Scenario.