The Spruce Goose: Howard Hughes’ H-4 Hercules

The Spruce Goose is the largest flying boat ever built, and it flew exactly once. On November 2, 1947, Howard Hughes lifted the eight-engined wooden giant off Long Beach Harbor for less than a minute, and it never left the water again.

Its real name is the Hughes H-4 Hercules. It has a wingspan of 319 feet 11 inches (97.51 m), which is wider than a Boeing 747, wider than an Airbus A380, and wider than the Antonov An-225. That record stood for 72 years.

It was not made of spruce, it was made of birch. It was not really Howard Hughes’ idea, and it was not a failure in the way people usually mean. Here is the full story, with the specifications verified and the disputed numbers laid out honestly.

Question	Answer
Proper designation	Hughes H-4 Hercules (originally HK-1)
Wingspan	319 ft 11 in (97.51 m)
Number built	1
Times flown	Once, on November 2, 1947
Flight duration	About 26 to 30 seconds
Pilot	Howard Hughes
Made of	Laminated birch (Duramold), not spruce
Where it is now	North American Aerospace Museum, McMinnville, Oregon

What Was the Spruce Goose?

The Spruce Goose was a prototype heavy transport flying boat built by the Hughes Aircraft Company during and after World War II. Its formal designation is the Hughes H-4 Hercules.

The job it was designed for was simple and urgent. German submarines were sinking Allied shipping in the North Atlantic faster than the shipyards could replace it, and troops and cargo still had to reach Britain.

The proposed answer was to fly the cargo over the submarines instead. The aircraft was specified to carry 750 fully equipped troops, or two M4 Sherman tanks, across the ocean in one lift.

Who Actually Came Up With It?

The concept belonged to Henry J. Kaiser, the industrialist behind the mass-produced Liberty ships. Kaiser proposed a fleet of enormous “flying cargo ships” and needed an aircraft builder to make them real.

Hughes supplied the engineering. The original designation, HK-1, stands for Hughes-Kaiser, and the 1942 contract called for three aircraft within two years.

Kaiser had no aeronautical experience and withdrew from the project well before it was finished. Hughes carried on alone under a new contract for a single aircraft, redesignated the H-4.

Where the Name Came From

“Spruce Goose” was never an affectionate nickname. It was coined by critics during the 1947 Senate War Investigating Committee hearings, and Republican Senator Owen Brewster of Maine used it as a weapon.

Hughes hated it, and he had a fair point: the aircraft is built almost entirely of birch. The name stuck anyway, which is why the most famous wooden aircraft in history is named after the wrong tree.

How Big Was the Spruce Goose?

Big enough that it still holds records almost 80 years later. The H-4 remains the largest flying boat ever built and the largest aircraft ever built from wood.

What it no longer holds is the wingspan record, and that is the measure that made it famous. For the wider question of which aircraft is the largest ever by each measure, see our ranking of the biggest aircraft in the world.

Hughes H-4 Hercules Specifications

Specification	Figure
Length	218 ft 8 in (66.65 m)
Wingspan	319 ft 11 in (97.51 m)
Height	79 ft 4 in (24.18 m)
Empty weight	About 250,000 lb (113,400 kg)
Maximum takeoff weight	400,000 lb (181,400 kg)
Engines	8 x Pratt & Whitney R-4360 Wasp Major, 3,000 hp each
Total power	24,000 hp
Propellers	4-blade Hamilton Standard, 17 ft 2 in (5.23 m) diameter
Design capacity	750 troops or two M4 Sherman tanks
Design cruise speed	250 mph (400 km/h), never demonstrated
Design range	3,000 miles (4,800 km), never demonstrated
Number built	1

Note the caveat in that caption, because most articles about the Spruce Goose leave it out. Cruise speed, range and service ceiling are all paper numbers.

The aircraft never climbed above roughly 70 feet (21 m) or travelled more than a mile. Every performance figure you will read for it is an estimate that was never tested.

Spruce Goose Size Comparison: Wingspan

Wingspan is where the H-4 dominates. Its wings are straight and enormous, while the big jets that came later used shorter swept wings, so they outgrew it in weight and payload long before they outgrew it in span.

#	Aircraft	Wingspan	Status
1	Stratolaunch Roc	385 ft (117 m)	Flying, hypersonic test carrier
2	Hughes H-4 Hercules “Spruce Goose”	319 ft 11 in (97.51 m)	Museum display
3	Antonov An-225 Mriya	290 ft (88.4 m)	Destroyed February 2022
4	Airbus A380-800	261 ft 8 in (79.75 m)	In service
5	Boeing 747-8	224 ft 7 in (68.45 m)	In service

The Antonov An-225 Mriya, the only aircraft that could outlift it, was destroyed at Hostomel Airport near Kyiv in February 2022. Only one aircraft has ever had a wider wingspan than the Spruce Goose.

Is a 747 Bigger Than the Spruce Goose?

It depends entirely on which measure you pick, which is why this question gets answered both ways online.

By wingspan, no. The Spruce Goose beats the Boeing 747-8 by roughly 95 feet (29 m), which is not a close contest.

By length and by weight, yes. A 747-8 is 250 ft 2 in (76.25 m) long against the H-4’s 218 ft 8 in (66.65 m), and its maximum takeoff weight of about 987,000 lb (447,700 kg) is nearly two and a half times the Hercules figure.

The same split applies to today’s airliners generally, which is worth keeping in mind when you compare it against the largest commercial airplanes flying now. The Spruce Goose is the widest of the old giants, not the heaviest.

What Was the Spruce Goose Made Of?

Almost the entire aircraft is wood. The only significant exceptions are the engines, the electrical systems, and the metal fasteners and fittings.

Wood was a wartime necessity, not an eccentricity. Aluminum was a strategic material in short supply, and a program this large could not be allowed to compete with fighter and bomber production for it.

Weight mattered too. The heavier the empty airframe, the less cargo it could carry across the Atlantic, and every pound saved was a pound of payload gained.

What Duramold Actually Was

Calling the H-4 a wooden aircraft undersells the technology. The structure is Duramold, a laminated composite developed by Virginius Clark for Fairchild Aircraft.

Thin birch veneers are soaked in resin, stacked, then pressed inside a mold at temperatures around 280 degrees Fahrenheit (138 C). The result is a molded structural panel, not a plank.

The birch veneer came from Roddis Manufacturing in Marshfield, Wisconsin. Hughes bought the Duramold rights for aircraft over 20,000 pounds outright, which tells you how committed he was to the process.

Duramold was one of several such processes, alongside Haskelite and Aeromold, and de Havilland used related wood composites in the Mosquito and the DH.91 Albatross. None of them scaled to heavy aircraft economically.

How Many Engines Did the Spruce Goose Have?

Eight. The H-4 was designed before jet engines were a practical option, so it uses the largest piston engines available: the Pratt & Whitney R-4360 Wasp Major.

Each R-4360 is a 28-cylinder air-cooled radial producing 3,000 horsepower, driving a four-blade Hamilton Standard propeller 17 ft 2 in (5.23 m) across. Eight of them give the aircraft 24,000 horsepower.

The One Flight: November 2, 1947

Nobody expected the aircraft to fly that day. The schedule called for taxi tests in Long Beach Harbor, checking how the hull handled on the water before any flight testing began.

Hughes had just returned from Washington, where the Senate War Investigating Committee had spent weeks attacking the program’s cost and his handling of it. He knew the aircraft was close to being cancelled.

Thirty-six people were aboard, including flight crew, mechanics, and invited reporters. Thousands more watched from the harbor.

On the last run of the day, Hughes advanced the throttles further than a taxi test required and the hull came off the water. He held it there briefly, set it back down, and taxied in.

It was, by any reasonable reading, a deliberate act in front of an audience Hughes had made sure was watching. It worked. The press coverage turned, and the aircraft that “would never fly” had flown.

How Long, How High and How Far Did the Spruce Goose Fly?

Here is where almost every article about the Spruce Goose quietly picks a side. The two most authoritative sources do not agree, and the disagreement is not small.

Measure	The museum that owns the aircraft	Most widely published figure
Altitude	25 ft (8 m)	70 ft (21 m)
Distance	Just under half a mile (0.8 km)	About 1 mile (1.6 km)
Duration	About 30 seconds	26 seconds
Speed	Not published	135 mph (217 km/h)

We have quoted both rather than pretending the question is settled. If you want the honest answer, it is that the aircraft was airborne for under half a minute, somewhere between 25 and 70 feet up, and covered between half a mile and a mile.

Did It Really Fly, or Was It Ground Effect?

This is the sharpest criticism of the flight, and it is technically fair. Ground effect is the cushion of extra lift an aircraft gets when it is flying within roughly one wingspan of a surface.

The Spruce Goose has a wingspan of 319 ft 11 in. At 70 feet, and certainly at 25 feet, it was deep inside its own ground effect the entire time.

So the aircraft flew, in the sense that it left the water under its own power and was supported by its wings. Whether it could have climbed away and sustained flight at altitude was never tested, and now never will be.

The hull design that let it sit on the water at all is worth understanding on its own; we cover the principles in our explainer on whether airplanes float on water and the differences between seaplanes and floatplanes.

Why Did the Spruce Goose Only Fly Once?

The short answer: the war it was built for had been over for two years, the contract was finished, and there was no longer any mission for it. The flight in 1947 was a demonstration, not the start of a test program.

Four things killed it, and none of them was a technical failure of the aircraft itself.

The mission disappeared. The H-4 existed to beat the U-boat threat in the North Atlantic. By late 1947 that threat had not existed for over two years.

The material shortage disappeared. Wood construction was a workaround for a wartime aluminum shortage. With aluminum freely available, there was no reason to build large aircraft out of laminated birch ever again.

Jets arrived. The H-4 was designed around piston engines and propellers. By 1947 jet propulsion was clearly the future of large aircraft, and eight Wasp Majors were already yesterday’s answer.

It took too long and cost too much. The 1942 contract wanted three aircraft in two years. It delivered one in five, at a development cost of about $23 million, roughly $270 million in today’s money.

It is not the only aircraft whose size outran its usefulness, a pattern we trace in our piece on airplanes that were too big.

What Happened to the Spruce Goose After 1947?

Hughes never flew it again, but he never let it deteriorate either. For nearly three decades he kept the aircraft in a climate-controlled hangar in Long Beach, maintained in flying condition.

A full-time crew of 300 workers, all sworn to secrecy, looked after it. That was reduced to about 50 by 1962, but the aircraft stayed airworthy, waiting for a flight that was never scheduled.

When Hughes died in 1976, the crew was disbanded and the hangar lease ran out. The Summa Corporation, the Hughes estate holding company, proposed cutting the aircraft up and donating sections to museums.

The Spruce Goose Dome in Long Beach

The aircraft was saved in 1980 by the Aero Club of Southern California, which put it on display beside the Queen Mary in Long Beach Harbor.

The building put up to house it was an enormous climate-controlled geodesic dome, and for twelve years it was one of the most recognizable structures on the Long Beach waterfront. Locals simply called it the Spruce Goose Dome.

The Walt Disney Company bought the dome and the Queen Mary in 1988, intending to build a waterfront resort called Port Disney. The plan collapsed in 1991 and Disney told the Aero Club the aircraft had to go.

The dome is still standing and still in use, now as the Long Beach Cruise Terminal operated by Carnival. A replica Spruce Goose hangs from the roof, along with the model built for the 2004 Howard Hughes biopic The Aviator.

The $1 Sale

The Aero Club put the aircraft out to bid in 1992, and the outcome is one of the odder transactions in aviation history.

Evergreen International Airlines of McMinnville, Oregon won it with a bid of one dollar, plus an agreement to assume the debts attached to the aircraft.

Money was not the deciding factor. Every other institution that bid, the Smithsonian included, wanted only sections of the aircraft. Evergreen was the only bidder committing to display it whole.

Moving it cost about $3 million, far more than the purchase. The aircraft was dismantled in October 1992, barged up the coast and through the Columbia and Willamette rivers, and arrived in McMinnville in February 1993 after 138 days and 1,055 miles.

Where Is the Spruce Goose Now?

The Spruce Goose is on permanent public display at the North American Aerospace Museum in McMinnville, Oregon, about 40 miles southwest of Portland.

If that name is unfamiliar, that is because it is new. The museum operated as the Evergreen Aviation & Space Museum for decades and rebranded in 2026 to reflect a broader educational remit. The aircraft has not moved and the collection has not changed.

It is the centerpiece of the main hangar, which was built around it. Restoration took eight years after the aircraft arrived, and the reassembled H-4 opened to the public on June 6, 2001.

Visitors can walk beneath the wings and, on some tours, see inside the cargo hold and flight deck. It shares the museum with an SR-71 Blackbird and an F-117 Nighthawk.

Could the Spruce Goose Ever Fly Again?

No, and the reasons are practical rather than sentimental.

The aircraft has not been maintained in flying condition since 1976. It was disassembled for the move to Oregon and reassembled as a static exhibit, with structural bracing added during restoration that a flying aircraft would not carry.

It also has nowhere to go. The museum hangar was built around the aircraft, it is a flying boat with no water access, and there is no certification path for a one-off 1947 prototype that never completed a flight test program.

Eight airworthy R-4360 Wasp Majors would be a serious undertaking on their own. The Spruce Goose has flown for the last time.