The chief technology officers (CTOs) of global major aerospace groups Airbus, Boeing, Dassault Aviation, GE Aerospace, Rolls-Royce, RTX (formerly Raytheon), and Safran have issued a joint statement calling for governments to increase their funding for research into the climate impacts of aviation’s non-carbon emissions. The statement was released at the 2024 Farnborough International Airshow, in the UK. (The CTOs also noted that their companies fully supported the civil aviation industry’s commitment to achieve net-zero CO₂ emissions by 2050.)

They pointed out that persistent contrails (condensation trails, created when water vapour emissions from jet engines condensed in the cold temperatures found at jet airliner cruising altitudes) were estimated to have a warming effect on the climate. But lack of data has meant that the estimates of their climate impact have been very uncertain. There is still not enough understanding of the atmospheric conditions, physical and chemical properties and mechanisms, that influence the formation and evolution of contrails.

Likewise, nitrogen oxide (NOx) emissions and their ancillary reactions were dependent on atmospheric conditions as well as the design and operating conditions of the engines. Again, more research is needed to accurately establish the interactions triggered by, and the impacts of, aviation NOx emissions.

“We jointly call for increased research funding to develop the science needed to underpin technology choices, operational changes and policy decisions,” urged the CTOs. “We will continue to engage academia, the global climate and weather modelling community, government organisations and industry partners to advance seven priorities for research.”

The seven priorities listed by the CTOs were – improve the understanding of contrail formation, persistence and climate impact; improve the understanding of emissions properties, for sustainable aviation fuels and hydrogen, as well as conventional jet fuels, and of the combustion characteristics of different engine technologies; develop research into aerosol cloud interactions; increase knowledge regarding the radiative impact, and modelling uncertainty, regarding NOx emissions; build understanding of aviation emission trade-offs and interdependence (covering CO₂, NOx, soot, contrails and noise); create and upgrade common models for quantifying aviation’s effects on climate; and, research into what impacts climate mitigation might have on airspace networks.

“As the industry aims to mitigate the impact of non-CO₂ emissions, we are unified in focusing our efforts on research, flight testing and data transparency to advance these seven priorities alongside our academic and government stakeholders,” they affirmed. “Through industry, academic and institutional stakeholders effectively working together, we can achieve meaningful progress toward a more sustainable aviation industry.”