Ask a Millennial what a dirigible is, and you’ll get a seriously blank look. Those of us old enough to appreciate the Goodyear Blimp (not the Hindenburg) have fond memories of them slowly air-lumbering around football stadiums. Well, their heyday might not be over quite yet if Varialift has anything to say about it. The UK-based company has built solar-powered versions that could revolutionize air freight. The big ships use solar power and jet engines and would use only 8% of the fuel used by cargo planes. In case you’re worried about highly combustible hydrogen dangers, these blimps use helium instead and benefit from strong and lightweight aluminum frames. Unfortunately, their reliance on solar power means they can’t operate at night, hampering some of their usability, but perhaps they’ll come up with a way to store some of that energy. What they do provide is more affordable construction, far less fuel, and drastically reduced emissions. But they are a lot slower than jets, which means you won’t see Amazon buy any for Prime duties.