The real issue is producing green hydrogen at an economic cost, until enough electricity is produced to do that hydrogen is not commercial, forget about off peak power that is all going to be used up with storage or charging EV batteries, that is twice as efficient as hydrogen. It may be that a way to produce hydrogen cheaply in the future, until then it’s just dreams.
Aviation produces a small part of CO2 emissions, when all surface pollution has been eliminated, the much more difficult aviation solutions will need to be addressed, that will be a very long time in the future