The aviation industry needs to reduce its climate impact. There are various research areas currently being investigated to accomplish this, such as the use of alternative fuels, the design of climate-optimized aircraft and/or aircraft designed for those fuels, and the use of operational mitigation strategies. This research focuses on the overlap of these three, examining the effect of alternative fuels and aircraft on a future airline through the use of climate impact taxes in a fleet allocation model. Kerosene and liquid hydrogen climate and cost-optimized aircraft are used in the fleet allocation for regional, small-medium, and long-range aircraft. Sustainable aviation fuel (SAF) allocation is incorporated through the possibility of adding a 50% SAF blend to the kerosene aircraft. This research calculates the climate impact of flights, including CO2 as well as non-CO2 climate effects, with the CLIMaCCF library using ERA5 reanalysis data from ECMWF. These calculations are provided as inputs to the fleet allocation model, which uses dynamic programming and examines the changes in the airline’s profit and overall climate impact for different levels of climate impact tax. The results find a Pareto front between the climate impact reduction and the overall profit, resulting in a climate impact reduction potential of 10-15% at the expense of around 1% profit loss, and around 50-60% at 20-30% profit loss. Increasing climate impact tax levels move the fleet composition through a transition from kerosene, to 50% SAF blend, to liquid hydrogen. The transition differs per aircraft category (regional, small-medium range, and long-range), and shows that the climate-optimized aircraft are scarcely used due to their increased flight time and flight costs, for all levels of climate impact tax.