HK-1
The HK-1 was called the “Spruce Goose” because it was almost completely made of birch. Originally, it was intended to be used during World War II as a transatlantic transport aircraft, though it was not completed in time. The U.S. military flew it once back in 1947, and just one prototype was built. The flight covered roughly one mile. It is displayed at Oregon’s Evergreen Aviation and Space Museum.
Blohm And Voss BV 238
Built during World War II, this German flying boat first took to the air in 1944. The Blohm and Voss BV 238 weighed 120,769 pounds empty, and it was the heaviest aircraft ever built during that time. Because of the resources needed to construct it, there was only one unit ever built. In addition, the aircraft was the largest of all the planes that the Axis powers produced during the war.