PtL fuels are broadly recognized as an important option to make aviation CO₂ neutral, and the industrial production of PtL fuels has moved within reach. The updated version of the background paper reviews the basic principles of PtL production routes and draws a comparison with competing fuel options based on sustainability criteria. In order to produce sustainable PtL fuels in the required quantities, it is necessary to use renewable electricity from solar and wind energy, alongside extensively available renewable carbon sources. Furthermore, economic considerations, the technical suitability of PtL fuels, the influence of synthetic fuels on pollutant emissions and high-altitude climate impact, as well as a potential ramp-up of PtL production capacities are discussed.