This chapter explores the production of sustainable aviation fuels (SAFs) from the hydroprocessing of liquid biomass fractions. Various liquid streams are derived from biomass, including bio-oil, Fischer–Tropsch (FT) wax, triglycerides, waste cooking oil, and terpenes. The challenges in converting these fractions are analyzed, such as oxygen removal and meeting industry standards for aviation fuels. It also examines catalytic processes such as hydrodeoxygenation (HDO), hydroisomerization, and hydrogenation, along with their roles in SAF production. Additionally, the chapter emphasizes the importance of sustainable hydrogen sources and the need for further research to develop cost-effective and environmentally friendly catalytic materials and processes. By optimizing these strategies, the aviation industry can move toward decarbonization and a greener future.