For those who, like me, got confused: Hydrogen requires more volume for the same energy as jet fuel, but even with that larger volume, it is lighter than the smaller volume of jet fuel.
Since it doesn't need to loft that weight, that lifting capacity can be used for cargo instead, thus also increasing the top-line income for performing the flight. Finally, locally produced LH2 will be cheaper per joule delivered than jet fuel, moreso after its carbon is taxed, and the carbon burned in transporting it to the airport.
It will take a while to get there, because it needs both new (or maybe retrofitted?) airframes, and new airport infrastructure, initially only at key international airports.
Not injecting CO2 directly into the stratosphere will be a side benefit.