It would be much harder to engineer: you'd need a hefty tank; cryogenic fuel handling to increase density and lower tank weight. Safety is critical on aircraft

It would be much harder to engineer: you'd need a hefty tank; cryogenic fuel handling to increase density and lower tank weight. Safety is critical on aircraft. Hydrogen is difficult to contain, and has very low viscosity due to its small molecules. It burns with an almost invisible yet very hot ultraviolet flame. It easily mixes with air to form an explosive mixture and has a very low minimum ignition energy (about a tenth of gasoline). Combustion of hydrogen in a heat engine for propulsion would be very inefficient compared to a battery electric. Fuel cells are in between, at about 40-60% efficiency, but have a substantial weight cost.