In 1942, at the height of World War II, Allied ships crossing the Atlantic were routinely attacked and sunk by German U-boats, interrupting shipments of supplies and troops to Europe.

The Allies needed a way to reliably and safely transport large payloads across the ocean. American industrialist Henry Kaiser lit upon the idea of a creating a cargo plane of unprecedented size, and turned to eccentric billionaire and aviator Howard Hughes to build it.

The plane would need to carry 150,000 pounds, 750 troops or two 30-ton Sherman tanks.

Originally designated the HK-1, the seaplane Hughes designed was absolutely massive. Weighing in at 300,000 pounds, with a wingspan of 320 feet, the plane was the largest flying machine ever built.

Because of wartime rationing on strategic materials such as aluminum, the plane was built almost entirely out of wood. A skeptical press dubbed it “The Spruce Goose.”

Hughes hated the nickname. He felt it was an insult to the prowess of his engineers, and an inaccurate one at that — the plane was made out of birch.

The construction of the plane dragged on, partly because of Hughes’s notorious perfectionism, and the war ended before the behemoth could be completed.

After Kaiser dropped out of the project, Hughes renamed it the “H-4 Hercules."