Pathways to net-zero emissions from aviation

International climate goals imply reaching net-zero global carbon dioxide (CO 2 ) emissions by roughly mid-century (and net-zero greenhouse gas emissions by the end of the century). Among the most difficult emissions to avoid will be those from aviation given the industry’s need for energy-dense liquid fuels that lack commercially competitive substitutes and the difficult-to-abate non-CO 2 radiative forcing. Here we systematically assess pathways to net-zero emissions aviation. We find that ambitious reductions in demand for air transport and improvements in the energy efficiency of aircraft might avoid up to 61% (2.8 GtCO 2 equivalent (GtCO 2 eq)) and 27% (1.2 GtCO 2 eq), respectively, of projected business-as-usual aviation emissions in 2050. However, further reductions will depend on replacing fossil jet fuel with large quantities of net-zero emissions biofuels or synthetic fuels (that is, 2.5–19.8 EJ of sustainable aviation fuels)—which may be substantially more expensive. Moreover, up to 3.4 GtCO 2 eq may need to be removed from the atmosphere to compensate for non-CO 2 forcing for the sector to achieve net-zero radiative forcing. Our results may inform investments and priorities for innovation by highlighting plausible pathways to net-zero emissions aviation, including the relative potential and trade-offs of changes in behaviour, technology, energy sources and carbon equivalent removals. Decarbonizing the aviation sector is difficult given travel patterns and technical and economic constraints. Through nine holistic scenarios towards net-zero emissions from aviation by 2050, this study can inform investments and priorities for innovation to achieve a more sustainable aviation sector.