Air transport is quite possibly the best use case for hydrogen fuel that I can think of, and likely the only way we'll get sustainable air travel in the near future.

Sometimes I wonder if that would end up being a solution for cars, too. It would certainly solve a few difficult edge cases that electrification will have a hard time overcoming.

Some synthetic fuel production processes require hydrogen, so a cheap hydrogen source would still be useful.

That brings up an interesting point. I wonder how much of a factor fuel is in dictating the preferred size for an airliner. Maybe if the fuel economics and physics change, we'll see an evolution towards larger numbers of smaller point-to-point airliners.