> what’s the barrier to creating fuel from air and water, using electricity? > it’s not really fossil fuels that are needed for planes and rockets, but high e

> what’s the barrier to creating fuel from air and water, using electricity? > it’s not really fossil fuels that are needed for planes and rockets, but high energy density liquid fuels The energy density of liquid hydrogen is really low, so that idea won't work. You want hydrocarbons of some sort, because they have the required energy density, so you could probably switch planes to run on some sort of biodiesel instead of fossil fuel.