Reading level:

B-377-SG/SGT Super Guppy

Aero Spacelines / Boeing · Outsize cargo aircraft · Early Jet (1946–1969)

B-377-SG/SGT Super Guppy — Outsize cargo aircraft
Open in interactive gallery →See aircraft like this on the live radar →

The Aero Spacelines Super Guppy is the second-generation outsize-cargo flying-fish derivative of the Boeing 377 Stratocruiser, built by Aero Spacelines from 1965 onward to haul oversized rocket stages between NASA centres during the Apollo programme. Five airframes were built across two variants — one piston-engined Super Guppy (SG) and four turboprop Super Guppy Turbines (SGT). One SGT, NASA 941 (registered N941NA), is still in active NASA service in 2026, ferrying International Space Station hardware between European, Japanese, and U.S. NASA facilities.

The Super Guppy was the larger successor to the smaller Pregnant Guppy, which Aero Spacelines founder Jack M. Conroy had built in 1962 to move Saturn S-IV stages from Douglas in Long Beach to Cape Canaveral. The Super Guppy was a more dramatic conversion: the entire upper fuselage was sliced away and replaced with a 25-ft-diameter pressurised "bubble" cabin sitting atop a massively reinforced lower fuselage frame. Cargo loaded through a hinged 110° opening of the entire forward fuselage — the airframe's nose, cockpit and all, swung sideways on hinges to expose the hold. The conversion produced a hold 25 ft (7.6 m) tall and wide, and 111 ft (33.8 m) long.

The Super Guppy SGT — which is what survives today — was a complete re-engine: the original Pratt & Whitney R-4360 Wasp Major piston engines (3,000 hp each) were replaced with four Allison 501-D22C turboprops (4,912 shp each), the same engine family used on the C-130 Hercules. The first SGT flew on 24 August 1970. Aero Spacelines built four SGTs through 1983; Boeing then took over the design and supplied two more for Airbus's continental cargo operations in Europe (which Airbus later replaced with its A300-600ST Beluga).

NASA 941 is the survivor that has flown longest in active service. Originally built for Airbus and registered F-BPPA, it was bought by NASA in 1997 and ferried out of Toulouse to Edwards AFB, then to El Paso for ISS hardware ferrying. As of 2026 NASA 941 continues to ferry pressurised modules, life-support systems, and propulsion components between Marshall Space Flight Center, Johnson Space Center, Kennedy Space Center, and contractor facilities in Italy and Japan. The Super Guppy's combination of outsize hold, slow flight envelope (cruise about 230 knots), and ability to operate from secondary airfields keeps it irreplaceable for NASA — there is no commercial alternative for its mission.

For Kids — a shorter, friendlier version

The Super Guppy is a very special cargo plane. It was built by a company called Aero Spacelines starting in 1965. Its job was to carry giant rocket parts for NASA's Apollo program.

The plane looks very strange and round on top. Workers cut away the upper part of a Boeing 377 airliner. Then they added a huge bubble-shaped cabin that is 25 feet wide. That bubble is bigger than most living rooms!

Loading cargo into the Super Guppy is amazing to watch. The entire nose of the plane swings open to the side. The cockpit moves with it. Then workers can slide in giant rocket parts through the front.

Five Super Guppies were ever built in total. One version had piston engines and four had turboprop engines. Only one is still flying today, and NASA uses it right now in 2026.

That flying Super Guppy is called NASA 941. It carries parts for the International Space Station. It flies between labs in Europe, Japan, and America to deliver these huge pieces.

Fun Facts

  • The Super Guppy's bubble cabin is 25 feet wide — bigger than a large school classroom.
  • The whole nose of the plane swings open 110 degrees to load cargo inside.
  • Five Super Guppies were ever built, and only one is still flying today.
  • NASA 941 is still an active working plane in 2026 — it never retired!
  • The Super Guppy was bigger than its earlier cousin, the Pregnant Guppy, which flew in 1962.
  • It carried rocket stages for the Apollo program that sent astronauts to the Moon.
  • The Super Guppy hauls International Space Station parts between countries around the world.
  • The plane was made from a Boeing 377 airliner that got a massive bubble top added on.

Kids’ Questions

Why does the Super Guppy look so round and puffy?

Workers cut off the top of a regular airliner and added a giant bubble cabin on top. This made the hold wide enough to fit huge rocket parts inside. The round shape is what gives it its funny fish-like look.

How do you load cargo into the Super Guppy?

The entire nose of the plane swings open to the side on big hinges. The cockpit swings open with it. Then workers can roll or slide large cargo straight in through the front of the plane.

Is the Super Guppy still flying today?

Yes! One Super Guppy called NASA 941 is still flying in 2026. NASA uses it to carry parts for the International Space Station. It travels between labs in Europe, Japan, and America.

Variants

Super Guppy (SG, piston)
Original 1965 conversion of the Boeing C-97J Stratofreighter. Four Pratt & Whitney R-4360 Wasp Major radials. One built. Used by Aero Spacelines and NASA for Saturn IB and Apollo CSM ferry duty 1965-1980.
Super Guppy Turbine (SGT)
Re-engined turboprop variant, four Allison 501-D22C turboprops. Four built between 1970 and 1983. NASA 941 (originally F-BPPA, ex-Airbus) still in active service in 2026.

Notable Operators

NASA
Single active operator since 1997. NASA 941 ferries ISS hardware between Marshall, Johnson, Kennedy, and contractor facilities globally. Operates from El Paso, Texas, with crews drawn from NASA Johnson Space Center.
Aero Spacelines (historical)
Original builder and 1965-1980 commercial operator. Flew NASA Apollo and Saturn rocket-stage ferry contracts. Sold the type's production rights to Tracor and then to UTA Industries.
Airbus Skylink (historical)
Operated two Super Guppy Turbines (F-BPPA, F-BTGV) from Toulouse 1972-1996 to ferry Airbus airliner fuselage and wing sections between European factories. Replaced by the Airbus Beluga in 1995-1996.

Frequently Asked Questions

Is the Super Guppy still flying?

Yes — NASA 941 (registered N941NA) is the only one in active service. As of 2026 it ferries International Space Station hardware between Marshall, Johnson, Kennedy, and contractor facilities in Italy, Japan, and Germany. It is operated out of El Paso, Texas, and the Johnson Space Center.

How does the Super Guppy load cargo?

The entire forward fuselage — nose, cockpit, and all — hinges open 110° to the side, exposing the entire 25-ft-diameter cargo hold. Crew has to disconnect the cockpit electrical connections from the rest of the aircraft before swinging the nose, then reconnect after closing. The arrangement is unique to the Guppy family.

What was the Super Guppy built from?

Boeing 377 Stratocruiser airframes (or their military C-97J Stratofreighter variants). The original tube fuselage was sliced away just above the floor; a new 25-ft-diameter "bubble" upper section was built on top of the reinforced lower fuselage. Wings and lower fuselage are largely original 1940s Boeing structure.

How is the Super Guppy different from the Pregnant Guppy?

The Pregnant Guppy (1962) was the smaller predecessor, built to ferry Saturn S-IV stages — about 20 ft hold diameter. The Super Guppy (1965) was a much more aggressive conversion with a 25-ft hold for Saturn S-IVB stages. The Mini Guppy (1967) was a third intermediate-size design.

Why hasn't NASA replaced the Super Guppy?

No commercial freighter has the Super Guppy's specific 25-ft hold diameter — most outsize-cargo freighters are limited by their original tube-fuselage diameter. The Airbus Beluga and BelugaXL serve the same niche in Europe but are tied to Airbus's own fleet. NASA could lease commercial Beluga services but currently finds NASA 941 cheaper to operate.

Sources

See Also