&gt;And in terms of energy cost, large classical airships like the ones that flew in the 1930s are just barely cheaper than the most efficient cargo planes...<p>This, I think, is simply wrong, though I&#x27;d be happy to look at numbers to the contrary.  Unless, of course, he&#x27;s trying to compare <i>actual</i> airships from the &#x27;30s to today&#x27;s cargo planes.