Exactly. There are already restrictions for transport of other hazardous goods. (EDIT: Finding sky routes should certainly be easier than finding restricted road routes) I'm also not sure that the biggest risk of a hydrogen explosion isn't simply the dropping of the cargo. Hydrogen explosion up in the sky is likely to burn upward and quickly. As long as the cargo or airframe isn't also burning, it seems likely the fire would never reach the ground.

Yes, but the Hindenburg was basically already on the ground (coming in for a landing) when it went up. Also, I remember reading that the airframe itself was pretty flammable.

Additional safety at terminals seems prudent, but would a non-flammable airframe still be burning on the ground if it caught fire at 10,000 feet? I don't know.

Considering the nature of hydrogen that would be totally dependent on the availability of O2 in surrounding compartments.

> the Hindenburg was fortunate in that when it came down it wasn't over, say, Manhattan

No, it wasn't really "fortunate" that a disaster which seems most likely to have been (based on the credible hypotheses for the cause) immediately related to landing operations happened exactly at a landing field and not somewhere else.