Hydrogen is certainly viable, but it will take a long time to build out the equipment to produce enough of it. Every last kg produced will be spoken for. Once

Hydrogen is certainly viable, but it will take a long time to build out the equipment to produce enough of it. Every last kg produced will be spoken for. Once LH2 aircraft enter any route, kerosene craft will suddenly be wholly unable to compete. But it needs abundant renewables, and synthesis equipment and underground tankage at airports.