Non-CO2 emissions

Burning jet fuel creates both carbon dioxide (CO₂) and non-CO₂ emissions. Non-CO₂ emissions consist mostly of water vapour and soot.

At altitude, in certain conditions water vapour freezes around soot particles. This forms ice clouds known as condensation trails, or contrails - the white streaks behind aircraft in flight.  

Calculating contrails’ climate effect is complex. It depends whether they are persistent, when and where they are formed and whether they have a cooling or warming effect: contrails both reflect incoming solar radiation and trap outgoing heat.

This Airbus-led project within the EU’s SESAR programme is assessing the impact that atmospheric conditions, aircraft characteristics and fuel have on non-CO₂ emissions. This includes how contrails could be mitigated through adapted flight operations to reduce aircraft-induced climate impacts.

The PACIFIC consortium brings together 11 partners from four countries to investigate the impact of fuel composition and engine cycle on particle emissions at different scales. 

PACIFIC seeks to bridge the gap in understanding aviation’s non-CO₂ emissions by testing an unprecedented range of fuels under controlled conditions. PACIFIC will ensure consistency in combustion parameters and hardware similarity from lab-scale experiments to full aircraft engine tests. The multiyear project launched in January 2025.