The article discusses the slow progress in developing alternatives to hydrocarbon propulsion systems for Air Transport. It covers the challenges faced by full hybrid propulsion systems due to complexity, weight, and cost, noting that mild hybrid concepts like the Volt Aero Cassio aircraft show promise in reducing fuel burn and pollution. Engine mild hybrids with auxiliary gearboxes are also explored, offering a 5% increase in engine efficiency with minimal complexity investments. The discussion then shifts towards the latest trends in hydrogen-fueled propulsion systems. Pratt & Whitney's advancements in gas turbine hydrogen-burn technology are highlighted for virtually eliminating NOx emissions and enhancing end-to-end efficiency. Additionally, fuel cell-based systems utilizing hydrogen to produce electricity are mentioned, with progress made in developing lighter and more efficient fuel cell technologies. The article concludes with a plan to delve deeper into hydrogen developments in upcoming segments, starting with hydrogen burn technology and exploring new innovative ideas in the field.