Boeing C-97/KC-97 Stratofreighter

Updated: October 2026 – Four radial engines, a tall tail and a fuselage that looks as if someone had stacked two aircraft on top of each other: that is the Boeing C-97 Stratofreighter – or, with a refueling boom under the tail, its tanker version, the KC-97. It was the transport and tanker of the US Air Force in the first years of the jet age. Here you learn how the C-97 came out of the B-29, how to tell it from its civil sister, the 377, and where you can still see one today.

What is the Boeing C-97/KC-97 Stratofreighter?

The C-97 is a four-engine long-range transport from Boeing, internally designated Model 367. The idea was as simple as it was effective: Boeing took the wings, tail, landing gear layout and engine nacelles of the B-29 Superfortress and put a new, much more voluminous fuselage on top. The lower fuselage roughly corresponds to the slim bomber fuselage, with a second, larger fuselage section above it. In cross section that gives the typical shape of a figure eight on its side, called the “Double Bubble”. The fuselage was pressurized – a big step for a transport of the 1940s.

The XC-97 prototype made its first flight on November 9, 1944, still with the Wright R-3350 engines of the B-29 and the bomber’s shorter vertical stabilizer. For production, Boeing then adopted the more powerful Pratt & Whitney R-4360 Wasp Major and the tall tail of the B-50, the development of the B-29. This combination defines the look of almost all later examples.

The pure transports remained a modest series: counting pre-production aircraft, C-97As and C-97Cs, 77 aircraft came together. The tanker became far more important: 811 examples of the KC-97 were built, 592 of them alone in the main version, the KC-97G. Together that is around 888 aircraft. From the same basic design, Boeing also derived the airliner Boeing 377 Stratocruiser, which first flew in 1947.

The versions at a glance

For spotters in museums, the tankers and the tankers converted back into transports are the most relevant. The designations often change: many aircraft first served as KC-97Gs and later as C-97Gs.

Version	Number	Feature
XC-97	3	Prototypes with R-3350 engines and the short B-29 tail
YC-97 / YC-97A / YC-97B	pre-production	Testing, YC-97B as a passenger version with 80 seats
C-97A	50	First production transport with Wasp Major engines
C-97C	14	Strengthened cargo floor, in Korea as an ambulance aircraft (MC-97C)
KC-97E	60	First production tankers with Flying Boom
KC-97F	159	More powerful R-4360-59B engines
KC-97G	592	Main version, additional tanks under the wings, usable as a tanker or transport
KC-97L	81 conversions	KC-97G with two additional J47 jet engines
C-97G / C-97K / HC-97G	conversions	Former KC-97Gs as transports, troop carriers and rescue aircraft

An oddity is the YC-97J: two KC-97Gs received Pratt & Whitney turboprops instead of the radial engines. Further conversions did not happen because the air force had already shifted to the pure jet tanker.

The three features that are enough to identify it

The final certainty comes from the serial number on the tail, usually in abbreviated form on US aircraft. How to read these numbers and derive the year of manufacture and the individual aircraft from them is explained in the guide US military serials.

KC-97, Boeing 377 or B-29?

The family ties within the Boeing family make identification exciting. The finder helps narrow it down.

A special case are the aircraft of the Israeli air force: it converted former 377 airliners into transports and in part combined them with the tail of the C-97, complete with cargo door. Such hybrids can be assigned cleanly only through the history of the individual aircraft. The four-engine Douglas C-54 Skymaster from the same era, by contrast, is easy to rule out: it has a single-deck, slim fuselage and a much smaller tail.

The C-97 as a transport: airlift, Korea, Biafra

The first C-97s joined the US Air Force in the late 1940s. During the Berlin Airlift, a single YC-97A flew supply flights to Berlin in April 1949. Landing gear damage on landing at Gatow put it out of action, and the blockade was over before the repair was finished. The story of the airlift is told in the article The Berlin Airlift 1948/49; you can visit the historic airfield of the time today at the Military History Museum Berlin-Gatow.

In the Korean War, C-97Cs flew out wounded as ambulance aircraft, designated MC-97C. Later, retired aircraft passed into civilian hands. In the late 1960s, C-97Gs flew in the relief airlift to Biafra during the Nigerian civil war at night and at low level to the improvised Uli airstrip; at least two were lost in the process. One of the aircraft used at the time, formerly registered with the Swiss airline Balair, is according to inventory lists now at the Pima Air & Space Museum.

The KC-97 as a tanker: between the propeller and jet eras

The design found its real role as a tanker. From 1951 the KC-97 flew with Strategic Air Command, mainly to refuel the new B-47 Stratojet bombers in the air. The heart of it was the Flying Boom: a rigid, steerable boom under the tail that the boom operator, lying down, guided through a window in the tail into the receptacle of the receiver. The principle came from tanker conversions of the B-29 and lives on to this day in the KC-135 and the KC-46 Pegasus.

A special feature was the fuel logistics: the kerosene supply for the jets was stored in tanks in the lower deck, the aviation gasoline for the aircraft’s own piston engines separately from it. The upper deck remained usable for cargo, so the KC-97G could serve as a transport without conversion.

The basic problem was speed. A piston-engine tanker flies much slower and lower than a jet bomber. During refueling the receivers had to slow down considerably – B-52 crews even extended flaps and parts of the landing gear to do so. From 1956 the KC-135 therefore gradually replaced the KC-97.

A late chapter: the Air National Guard and Europe

After leaving active service, many tankers went to the Air National Guard and the Reserve. As part of Operation Creek Party, National Guard tankers flew missions in Europe for about ten years from 1967, refueling units of the US Air Force and NATO. In June 1978, the KC-97’s service in the US ended for good; the last units switched to the C-130 and KC-135.

Some foreign air forces also flew the type. Spain took over three former US tankers in the early 1970s, and Israel used KC-97s and converted 377s as transports and tankers. In September 1971, Egyptian surface-to-air missiles shot down an Israeli aircraft near the Suez Canal.

A detail for Frankfurt insiders: the KC-97L in the museum in Dayton carries the name “Zeppelinheim” – like the district right at Frankfurt Airport after which the Zeppelinheim viewing platform is also named. The background to the name is best read on site on the museum placard.

Legacy: Guppys and the Super Guppy Turbine

A family of its own emerged from the components of the C-97 and 377: the Guppys of Aero Spacelines. The first Super Guppy was built from a retired YC-97J whose fuselage was lengthened and greatly widened. The later Super Guppy Turbine took over the cockpit, wings, tail and main landing gear of the 377 family but got a completely new fuselage. Airbus used such aircraft from the 1970s to fly components to Toulouse, before the A300-600ST Beluga took over the task. A Super Guppy Turbine still flies for NASA today.

The C-97 and KC-97 in museums

More than two dozen examples survive, some of them in storage, the great majority in the US. According to inventory lists, these addresses show a C-97 or KC-97:

• National Museum of the US Air Force, Dayton: the KC-97L “Zeppelinheim”; described as a spot under Dayton.
• Pima Air & Space Museum Tucson: Stratofreighters in the large outdoor area – more on the spot under Pima Air & Space Museum.
• Museo del Aire Madrid: a former tanker of the Spanish air force; as a spot under Museo del Aire in Cuatro Vientos.
• Other US museums: among them the Air Mobility Command Museum in Dover, the Castle Air Museum in California and the March Field Air Museum in Riverside.
• Israel: a KC-97G in the Israeli Air Force Museum near Be’er Sheva.

Exhibits are rebuilt, aircraft moved or restored. Find out before your visit whether the aircraft is currently accessible. Some airframes are also in storage with private owners – how to classify such storage areas is covered in the article Aircraft graveyards and boneyards.

Photo tips for the C-97 and KC-97

A parked giant with a double fuselage is a rewarding but unwieldy subject. A few points help.

You can work out in advance when the light is right with the guide Planning the sun position for your photo spot. If you do catch the flying “Angel of Deliverance” someday, Photographing propellers helps you with the right shutter speed. A broader introduction to identifying old types is provided by Spotting vintage aircraft in the sky and Identifying military transports. How rare your sighting is, you can judge with Judging the rarity of a sighting.

Commonly confused types and how to rule them out

Conclusion

The C-97/KC-97 Stratofreighter shows how much Boeing got out of the B-29: first a pressurized, large-capacity transport, then the standard tanker of the early jet era and, via the 377, even a luxury airliner. Double fuselage, four radial engines and the tall tail make it unmistakable, the refueling boom gives away the KC-97, the jet nacelles the KC-97L. Flying, it is an absolute rarity today; in museums you meet it mainly in the US and in Madrid.