This paper presents the main results of a fleet-level assessment of H₂-powered aircraft defined within the H2Avia research project, focusing on their energy performance and climate impact. The assessment is based on a global, long-term fleet evolution framework using scenario-based inputs for an in-house model which applies linear optimization to minimize the energy component of direct operating costs and the climate impact of a global fleet. Different transition scenarios from fossil-based aviation toward an H₂-powered aviation system are evaluated. The main findings show that H₂-based scenarios result in up to 15% higher block energy consumption at the fleet level compared with an SAF-based baseline in 2050, while providing the highest potential for a climate impact reduction of up to 60% relative to the same baseline. However, this benefit depends strongly on the inclusion and modeling of non-CO₂ effects for hydrogen, as well as on the weighting between energy cost and climate impact-driven objectives. The findings demonstrate the added value of an integrated assessment framework for capturing long-term fleet evolution and enabling rapid evaluation of emerging aircraft technologies in support of climate-neutral aviation strategies.

This paper presents an integrated assessment of liquid hydrogen as an aviation energy carrier, covering fuel production, aircraft performance, and fleet-level climate impacts. The results, based on the H2Avia research project, indicate substantial potential for reducing life-cycle global warming impacts compared to conventional kerosene. The analyses conducted for the interdisciplinary assessment are presented. The analysis shows that the use of liquid hydrogen eliminates CO₂ emissions during fuel burn, resulting in a significant reduction in global warming potential compared to conventional kerosene, despite remaining upstream emissions from production and transport. The aircraft application cases and the applied technologies assessment scenario are described. The modeled technologies essential for the hydrogen aircraft are discussed, and exemplary values are given. Integrated overall aircraft performance results are given and discussed. At the aircraft level, hydrogen-based aircraft require an 8–18% increase in design mission block energy compared to a 2040 kerosene baseline yet still achieve a reduction in effective global warming potential of 55–86% comparing a representative pair route between Europe and North America (6730 km). An overview of the fleet modeling approach and the applied scenarios is given. For a scenario with energy cost and climate impact as equally weighted minimization goals, the global fleet analysis yields a global warming potential reduction of 60% compared to the non-liquid hydrogen baseline scenario. Overall, the results suggest that liquid hydrogen-powered aircraft can deliver significant mission- and fleet-level reductions in global warming potential and thus represent a promising pathway for achieving long-term aviation climate targets.