MIT researchers are pioneering a sodium-based fuel cell for electric aviation, boasting energy densities up to five times greater than traditional lithium-ion batteries. The innovative system uses molten sodium as fuel, a solid electrolyte for ion transfer, and a foam cathode, eliminating the need for heavy hydrogen tanks. This breakthrough promises more efficient and sustainable long-haul electric flights, potentially reshaping the aviation industry. The technology captures carbon dioxide and could aid in ocean deacidification by producing sodium bicarbonate. Challenges persist, such as low power density and environmental impacts, which require further exploration. Propel Aero, a startup, aims to address these challenges and commercialize the technology for widespread adoption in the aviation sector.