Climate fact
Sustainable aviation fuel (SAF)
Sustainable aviation fuel (SAF) is a lower-carbon alternative to fossil jet fuel, made from renewable sources rather than crude oil. It's a "drop-in" fuel, meaning it can be blended into or used in place of conventional jet fuel without requiring changes to existing aircraft or airport fuel infrastructure.
How much it cuts emissions
Switching to SAF can cut a flight's direct fossil fuel emissions, meaning TTW and WTT combined, by up to 80%, since it produces significantly less carbon over its lifecycle than fossil jet fuel.
A flight's full climate impact is made up of three parts:
- TTW (tank-to-wake) — CO₂ from burning the jet fuel itself.
- WTT (well-to-tank) — upstream emissions from extracting, refining, and transporting the fuel.
- RFI (radiative forcing index) — extra warming from contrails and high-altitude NOₓ, expressed as CO₂-equivalent.
Read our methods page on how we calculate flight emissions.
What SAF doesn't cover
Even after switching to SAF, some climate impact remains: a smaller residual from producing the biofuel itself, and the RFI effects above, since switching fuel type doesn't change the physics of flying at altitude. Addressing what's left typically means funding certified climate projects, such as Gold Standard projects, rather than removing it directly.