A new paper has proposed a revolutionary idea for powering electric airplanes with liquid sodium metal in fuel cells, offering exceptional energy-to-weight ratios. While electric airplane companies have made progress in producing models for short distances, the challenge of decarbonizing long-distance travel persists. Professor Yet-Ming Chiang and colleagues from Massachusetts Institute of Technology advocate for using liquid metal sodium in fuel cells to enable cross-continental flights. The fuel cell's chemistry could potentially reduce aviation emissions by converting sodium oxide into sodium bicarbonate, actively removing carbon dioxide from the atmosphere. The technology, which stores significant energy when mixed with air at controlled humidity, shows promising results for regional flights. Challenges include scaling the production of sodium metal at an affordable price and addressing the release of sodium oxide. A spin-off company, Propel Aero, aims to further develop and test the technology for potential applications in electric aviation. While the use of liquid sodium in fuel cells presents a positive outlook for sustainable aviation, challenges such as production scalability and cost remain key considerations. The potential for reducing aviation emissions and achieving higher energy storage efficiencies makes this technology an exciting prospect for the future of electric airplanes.