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.
  • 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
Reduces CO2 effects but effectiveness and quality of compensation variable and difficult to verify
Avoiding areas where contrails are formed
Slight increase due to change of course
Slight increase but possible decrease with lower altitude


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
Slight decrease due to fuel savings
Little or no effect?
Slight decrease due to fuel savings


More constraints on flight planning and air traffic management
De-aromatized fuel
Small decrease during flight but potential increase during production
Reduced radiative effects in the absence of aromatics?


Introduction of a new fuel category
CO2 reduction compared to kerosene (life cycle)
Reduced radiative effects in the absence of aromatics?


Availability of sustainable biomass for production, investment and scale-up of the industry, cost.
15-25 years
Potentially neutral if made from atmospheric CO2 and decarbonised electricity
Reduced radiative effects in the absence of aromatics?


Technological maturity, energy efficiency and the need for decarbonised electricity, cost.
Potentially CO2 neutral if made from low-carbon energy sources
More frequent? But potentially lower optical thickness and shorter life?

Very high

Complete redesign of aircraft and refuelling infrastructure. Associated investment. Production development. Cost.
>30 years