The specific energy (mass energy density) of pure hydrogen is 3x higher than the next best hydrocarbon fuel. It doesn't have the best volumetric energy density,

The specific energy (mass energy density) of pure hydrogen is 3x higher than the next best hydrocarbon fuel. It doesn't have the best volumetric energy density, but it could be good enough as liquid hydrogen. The big pushback with liquid hydrogen is that everybody thinks you need to have cryogenic storage. That's a lie. Mildly insulated tanks would work extremely well, as the fuel consumption rates of aircraft would easily exceed the evaporation rates of the fuel. It might be problematic if they sit on the runway for hours waiting for takeoff, but as long as the plane is flying, liquid hydrogen is a pretty damn good fuel.