Technological challenges

Aviation must reduce its CO2 emissions..

The aviation industry anticipates three categories of technological solutions to reduce its carbon dioxide emissions.

  • Improving the energy efficiency of aircraft
    • By improving their aerodynamics (long wing span, active wing) to improve lift and reduce drag.
    • By reducing their weight (composite and functional structure).
    • More efficient propulsion systems (e.g. RISE programme).
  • Reduction of emissions associated with operations
  • Use of new fuels
    • Sustainable Aviation Fuels (SAF) (electrofuels or biofuels) have a chemical composition close to that of kerosene and can be used without drastic modification of the infrastructure. But they will have to be produced in the necessary quantities (thanks to decarbonised electricity, in the case of electrofuels) and certified.
    • Another approach, which involves a more profound change in supply logistics and aircraft design, is hydrogen (for example, the Airbus ZEROe programme).

.. without forgetting non-CO2 effects

There are three main non-CO2 effects:

  • Condensation trails (contrails): These contrails are the most visible mechanism. They 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.

  • Nitrogen oxide (NOx) emissions : 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.

  • The interaction of emitted particles with natural clouds: 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.

Technical solutions to reduce the climate impact of aviation

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