I don't really understand why hydrogen is not used for this, except the obvious historical connotations. Airplanes are full of highly flammable jet fuel, nobod

I don't really understand why hydrogen is not used for this, except the obvious historical connotations. Airplanes are full of highly flammable jet fuel, nobody suggests that they must run on non-flammable fuel. Of course one would need to take appropriate safety measures, probably some combination of compartmentalization of the bladder and controlled release (away from passengers) in the case of an ignition, but it seems like something that should be solvable with modern engineering.