Still need internal combustion, for air transport as well as space transport, folk should keep that in mind.
Not so well publicised, thus not so well known, is that burning green hydrogen in them reverses their action, from emitting toxins to cleaning them up, literally hoovering them out of both air and water, and the heat lost is still less than the heat from the sun that would have occurred if we didn't convert it instead to hydrogen in the first place.