Howard Hughes's H-4 Hercules, nicknamed the "Spruce Goose" by critics who never expected it to fly, was conceived in 1942 to transport troops and materiel across the Atlantic without the U-boat threat. The government funded the project with $18 million. Hughes insisted on building it of wood—birch, not spruce—because aluminum was rationed for conventional aircraft. The H-4 had a wingspan of 320 feet, still the longest of any aircraft ever built. It had eight engines, a hull shaped like a ship, and room for 700 troops. It was completed in 1947, two years after the war ended. On November 2, 1947, with Hughes at the controls, the H-4 made an unplanned flight during taxi tests in Long Beach Harbor. It lifted off, flew one mile at 70 feet altitude, and landed. It never flew again. Hughes kept it in a climate-controlled hangar until his death in 1976. It is now displayed at the Evergreen Aviation & Space Museum in Oregon, a monument to ambition and the limits of wood and ambition.