I don’t think that’s true, see the graph from this article: http://blogs.scientificamerican.com/guest-blog/helium-hokum-why-airships-will-never-be-part-of-our-transportation-infrastructure/
I don’t think that’s true, see the graph from this article: http://blogs.scientificamerican.com/guest-blog/helium-hokum-why-airships-will-never-be-part-of-our-transportation-infrastructure/