You can regenerate hydrogen in flight by (1) condensing water from the air and (2) electrolyzing it. It's so much cheaper and more replenishable than helium tha

You can regenerate hydrogen in flight by (1) condensing water from the air and (2) electrolyzing it. It's so much cheaper and more replenishable than helium that it allows much more flexibility and, ultimately, flight safety, because it can be vented in an overpressure emergency without any hesitation.