The aviation industry is a cornerstone of global transportation but significantly contributes to greenhouse gas emissions, necessitating a shift toward sustainable energy solutions. This chapter examines hydrogen and fuel cell technologies as transformative approaches to decarbonizing aviation. It begins by exploring the aviation ecosystem and identifying opportunities for reducing emissions, emphasizing the adoption of hydrogen as a sustainable energy carrier. The discussion delves into alternative fuels, with a focus on the potential of hydrogen-based solutions and their advantages over traditional fossil fuels. The integration of fuel cells, particularly solid oxide fuel cells, is presented as a promising technology for ground operations and aircraft systems. Advanced energy management strategies are introduced as essential tools for optimizing hybrid powertrain performance, ensuring efficient energy distribution, and enhancing system longevity. The final section presents a detailed case study of the NASA X-57 Maxwell electric aircraft, comparing single-stack and multi-stack fuel cell systems through simulation. The results highlight the operational and economic benefits of multi-stack configurations, showcasing their potential in achieving cost-effective and sustainable aviation solutions. This chapter provides a comprehensive framework for advancing hydrogen and fuel cell technologies, emphasizing their critical role in transitioning the aviation sector toward a greener future.