> Liquid hydrogen has about four times the volume for the same amount of energy of kerosene based jet-fuel. In addition, its highly volatile nature precludes storing the fuel in the wings, as with conventional transport aircraft. Therefore, most liquid hydrogen aircraft designs store the fuel in the fuselage, leading to a larger fuselage length and diameter than a conventional kerosene fuelled aircraft. This lowers the performance due to the extra wetted area of the fuselage. The larger fuselage size causes more skin friction drag and wave drag. On the other hand, hydrogen is about one-third of the weight of kerosene jet-fuel for the same amount of energy. This means that for the same range and performance (ignoring the effect of volume), the hydrogen aircraft would have about one-third of the fuel weight. For a Boeing 747-400 type aircraft, this would reduce the takeoff gross weight from 360,000 to 270,000 kg (800,000 to 600,000 lb). Thus, the performance of a hydrogen-fueled aircraft is a trade-off of the larger wetted area and lower fuel weight. This trade-off depends essentially on the size of the aircraft. [1]
From what I understand a considerable amount of the weight savings for H2 is lost when you add in the mass of the fuel tanks and piping.
The other problem is that the reduction in wing area needed (due to lower weight) is offset by the increase in drag of the fuselage so the savings are modest if they even materialize.
[1] https://en.wikipedia.org/wiki/Hydrogen-powered_aircraft#Prop...