Sustainable aviation fuel (SAF) is emerging as the leading way to reduce carbon emissions from the world’s vast commercial aviation sector, with California becoming North America’s leading testbed. The potential is large, but SAF supplies are limited and costs are high. Even in best-case California, significant policy changes are needed for this promising fuel to reach full commercial potential.

Worldwide, commercial aviation contributes a small — but growing — percentage of transportation-related greenhouse gas (GHG) emissions. Over the last decade, airlines have taken successful action to reduce their GHG emissions, primarily by improving engine and aircraft efficiency, which proportionally reduces exhaust emissions of carbon dioxide (CO₂). However, this “fleet modernization” is reaching diminishing returns to reduce carbon emissions from the global jet fleet. Unlike ground vehicles, it is not yet practicable to build safe, commercially viable aircraft powered by combustion-free electric-drive technology.

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