Aviation is already a major and growing emitter. In Europe its emissions have doubled since 1990, and globally they could, without action, double or treble by 2050. The sector will have a substantial fuel demand well into the 2030s, 2040s and beyond, the period when our economy needs to increasingly decarbonise. This report puts forward measures to limit that fuel requirement, but ultimately the remaining and substantial fuel demand will need to have its carbon content eliminated. The process of cutting and then decarbonising that fuel demand is the focus of this report of Transport & Environment.