This working paper provides background and analysis to help identify how an effective policy for alternative aviation fuels could distinguish among fuels that can deliver deep greenhouse (GHG) reductions and those that cannot. It provides an overview of the life-cycle GHG emissions attributable to the production of sustainable aviation fuels (SAFs) from a variety of conversion processes and feedstocks. Taking into account each fuel pathway’s GHG emissions and other sustainability considerations, the analysis assesses which SAF pathways are likely to play a meaningful role in European climate policy.