Clean energies are key to enable the decarbonisation of aviation. Sustainable Aviation Fuels, both ''drop-in'' and ''non drop-in'' alternative fuels to conventional jet kerosene, are one of the main pathways explored today by the aviation community. Drop-in alternative fuels represents a major opportunity to reduce today's aviation carbon emissions. Synthetic fuels are among the most promising options. Also called power-to-liquid (PtL) or e-fuels, synthetic fuels are often considered a sustainable option in the long term, due to their low lifecycle emissions and other environmental impacts. Initiatives and uses have multiplied in recent years. However, they still represent a niche fuel type and major challenges need to be overcome in order to ensure their large scale development and deployment. These challenges include renewables energy production scaled-up, cost competitiveness and infrastructure widespread support.