Methane Airships, anyone?
Has anyone ever considered methane-filled airships? Inflammable, true, but a lot less prone to leaking than hydrogen, and less explosive. They even let us use the stuff to cook with.
It's lighter than air.
If the airship were fuelled part with its own methane and part with liquid hydrocarbon it could maintain correct bouyancy: loss of lift from burned methane = loss of weight from burned liquid fuel.
Methane can also be "compresed" without much pressure, into cold water, to yield methane hydrate or clathrate. A little warmth reverses the process. This might also be a useful property.
BTW the Hindenburg disaster was not primarily caused by hydrogen. The primary cause was an electrical discharge setting fire to the highly inflammable metallized-paper-and-dope outer skin. That fire then released and ignited hydrogen from the gasbags. Had the gasbags been helium-filled, the Hindenburg would still have burned and crashed, but not such a big fire. I'm fairly sure that a hydrogen-filled airship built with modern materials could be safe. Ish. Cheap flight in a third-world country sort of safe, anyway.