Although I think it is clear that hydrogen fuel cells don't make sense for passenger cars, perhaps a case can be made that they might make sense for some classes of airplanes. See The plane that runs on hydrogen and emits only water - CNN.com Of course the plane described in that article is a 4 person modified sailplane (glider) but you have to start somewhere. It's an interesting idea. The goal is, quote: "The team aims to use fuel cells to power small and medium-sized passenger planes, which could change regional air travel and provide an alternative to carbon-emitting airplanes, buses and trains." The energy density of batteries is well below -- I would guess by orders of magnitude -- what is needed to effectively power small commercial planes useful distances. Using a fuel cell to make electricity onboard you don't need to devote much weight to batteries. Yes you still need to expend energy creating the hydrogen, building fueling stations, etc. But likely it is better, in many ways, than refining oil into av gas or jet fuel.