Remember that discussion of hydrogen-powered trains and planes a few days ago? Here's a BBC article that hits the aviation side pretty well with some recent test flights. It's not all sparks and roses.

[www.bbc.com]

The comments about the amount of H2 needed to replace jet fuel is kind of telling as to why the conversion won't be easy. Similar issues would arise with H2 for large-scale rail operations. As with the e-planes, though, short-distance captive operations have much more potential for valid experiments.