I suspect this is most useful as PR
I think hydrogen is going to have a hard time competing with synthetic hydrocarbons because of the storage problems. Even liquid hydrogen requires much bigger storage tanks. Then you've got the weight and size of the insulation. If you don't liquify it, you've got to compress it, which again requires heavy tanks. Then you've got the much higher risks from leaks, especially during refueling.
Long distance flight must eventually become net-zero carbon, but I doubt that Rolls Royce would be doing this if EasyJet weren't paying for it, probably from their PR budget.
Biting the hand that feeds IT
