From Worldskyrace.com: “Buoyant Flight is an inherently efficient form of transportation. This is the main reason why skyships were so promising in the1920s when airplanes still seemed a speculative venture. While today they are forgotten by many, skyships were actually very successful. By 1937, commercial passenger skyships of the Deutsche Zeppelin Reederei (DZR) had flown over half a million passenger-hours and a total of 52 million passenger-km safely on regional, transoceanic, transcontinental and artic voyages.” Airships Environmental Impact – Reducing CO2