The Spruce Goose is the name commonly given to the US Hughes H-4 Hercules, an aircraft designed and built by the Hughes Aircraft company that was the largest flying boat, and one of the largest aircraft, ever built.

The aircraft was a true marvel in its time. It married an increasingly outdated technology (flying boats) to a massive airframe that required some truly ingenious engineering innovations.

In 1942, the US War Department was faced with the need to transport large amounts of war material and personnel to Britain. With German u-boats exacting a terrible price from allied shipping in the Atlantic, a requirement was issued for a plane that could traverse these deadly waters while carrying a large payload.

The aircraft was the brainchild of Henry Kaiser, who directed the Liberty ships program. He teamed with aircaft designer Howard Hughes to create what would become the largest aircraft ever built or even seriously contemplated at that time. When completed, it would be capable of carrying 750 fully-equipped troops or two Sherman tanks.

To conserve metal for the war effort, the plane would be built mostly of wood, hence the Spruce Goose moniker. It was also referred to as the Flying Lumberyard by critics who believed an aircraft of its size simply would not fly.

Development outlasted the war. In 1947, Howard Hughes was called to testify before Congress, which was eagerly eliminating war-era spending to free up Federal funds for domestic projects. Though he encountered skepticism and even hostility from the committee, Hughes remained unruffled. During a break in the hearings, he returned to California, ostensibly to run engine tests on the H-4. On November 2, 1947 with Howard Hughes personally at the controls, the Spruce Goose lifted off from the waters off Long Beach, reminaing airborne 70 feet off the water at a speed of 80 miles per hour for just under a mile.

Hughes had proved the critics wrong, but the justification for continued spending on the project was gone. Congress killed the Spruce Goose, which never flew again. It was carefully maintained in flying condition until Hughes's death in 1976.

Though the project was abandoned, the H-4 Hercules presaged the massive transport planes of the future. Aircraft such as the American Lockheed C-5 Galaxy and the Russian Antonov An-124 and An-225 owe their existance to the Spruce Goose, which proved that the physical and aerodynamic principles that made flight possible were not limited by the size of the aircraft.