This chapter examines the potential of hydrogen as a sustainable energy carrier for decarbonising the aviation sector. It analyses the key technological pathways for hydrogen utilisation, including direct use in fuel cells and combustion engines, as well as its role in producing synthetic fuels like Power-to-Liquid (PtL) kerosene. The analysis covers the relative advantages and challenges of these technologies compared to alternatives such as Sustainable Aviation Fuels (SAFs) and battery-electric systems. A critical assessment of infrastructure requirements, economic viability, and the current policy landscape is provided. The chapter concludes that hydrogen’s impact will be gradual and segment-specific, complementing rather than replacing SAFs/PtL fuels for fleet-wide decarbonisation before 2050, with its ultimate climate benefit contingent on the availability of low-carbon hydrogen and careful management of non-CO₂ effects.