Aviation must reduce its CO2 emissions
- Improvements to flight plans could reduce fuel consumption
- Using high-resolution wind data to optimise flight paths1
- Flying in V formation like migratory birds to save fuel2.
In formation, each bird benefits from the lift generated by the vortexes at the wingtips of leading birds. This updraft helps each bird to support its own weight, allowing them to save fuel and thus be able to fly further.
- Technological solutions
- Use of biofuel3,4,5
Biofuels are increasingly being used by the aviation sector to reduce CO2 emissions. Airbus and the DLR (German Aerospace Centre) are studying the emissions associated with the use of this new fuel, which would reduce fossil fuel consumption. However, for safety reasons, current jet engines are not allowed to run on more than 10% biofuel.
- Use of biofuel3,4,5
- Offsetting CO2 emissions
- This practice is becoming increasingly common among airlines and the International Civil Aviation Organization (ICAO) is implementing CORSIA (Carbon Offsetting and Reduction Scheme for International Aviation). But is offsetting really effective in reducing CO2 emissions from aviation?6,7,8

Technological difficulties and ethical issues
- As the number of passebgers grows each year but the time to reduce emissions rapidly decreases, the aviation sector faces several obstacles. There are technological problems: it is very difficult to find a substitute for keresoene, but there is also the inequality of travelers. One study estimates that 1% of travelers contribute to 50% of emissions and that no more than 4% of the population travel internationally in any given year.9
- Fighting climate change and working in the aviation sector are increasingly seen as contradictory. The original Swedish movement, “Flygskam”, which means “shame on flying”, is gaining momentum in the Nordic countries. In France, more and more students are concerned about the environmental issues related to air transport and some are questioning their future in the sector.10

Non-CO2 effects
- Among the non-CO2 effects, contrails are the most visible mechanism. These contrails can form after the passage of an aircraft (depending on the properties of the engine plume and the atmosphere). Some contrails may also evolve into induced cirrus clouds and persist for several hours. These induced cirrus clouds would have a greater impact on the climate than CO2 emissions alone. Thus, avoiding their formation would reduce the impact of aviation on the climate.11
- Aircraft engines, in addition to emitting CO2 and water, also emit nitrogen oxides (NOx). At high altitudes, NOx leads to a decrease in the concentration of atmospheric methane but to the formation of ozone. Both gases (ozone and methane) are powerful greenhouse gases. To date, it is estimated that the impact of NOx tends to warm the climate.
- Among the products of kerosene combustion are solid or liquid particles that result from incomplete combustion in the engine. These particles, called aerosols, can influence the clouds naturally present in the atmosphere. These effects of aerosols on natural clouds have been little studied and their impact on climate has not been quantified.

The solutions to reduce the climate impact of aviation12
Move the mouse over the table to get more information.
Technological and operational solutions | CO2 | Contrails/ Induced cirrus |
NOx | Deployment complexity | Timeframe for large-scale deployment |
Carbon offsetting | ![]() |
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Existing | |
Avoiding areas where contrails are formed |
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Medium Introduction of metrics to identify trade-offs between CO2 and non-CO2 effects to ensure a beneficial effect on the climate |
10-15 years |
Formation flights | ![]() |
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Medium More constraints on flight planning and air traffic management |
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De-aromatized fuel | ![]() |
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Medium Introduction of a new fuel category |
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Biofuels | ![]() |
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Medium Availability of sustainable biomass for production, investment and scale-up of the industry, cost. |
15-25 years |
Electrofuel | ![]() |
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High Technological maturity, energy efficiency and the need for decarbonised electricity, cost. |
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Hydrogen | ![]() |
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Very high Complete redesign of aircraft and refuelling infrastructure. Associated investment. Production development. Cost. |
>30 years |
Sources
- How can high resolution wind data reduce CO2 emissions from flights?
- Airbus and its partners demonstrate how sharing the skies can save airlines fuel and reduce CO2 emissions
- ‘Significant milestone’: United Airlines flies passenger aircraft using 100 per cent biofuel engine
- First in-flight 100 percent sustainable-fuels emissions study of passenger jet shows early promise
- The aerial dance of DLR’s Falcon 20E and #A350 operating on 100% SAF
- Offsetting CO2 Emissions with CORSIA
- Climate-neutral flight through carbon dioxide offsets – an interim solution
- Planter des arbres pour compenser l’avion ?
- The six problems aviation must fix to hit net zero
- Dans les écoles d’ingénieurs aéronautiques, la « déprime existentielle » des étudiants
- Contrails: How tweaking flight plans can help the climate
- Updated analysis of the non-CO2 climate impacts of aviation and potential policy measures pursuant to the EU Emissions, European Union Aviation Safety Agency (EASA), 2020