The Boeing Model 377 Stratocruiser was a commercial transport development of the Model 367 (military C-97), and based on the improved-structure YC-97A with Pratt & Whitney R-4360 engines. The first flight of the prototype Model 377-10-19 was made on 8 July 1947, and it was delivered subsequently to Pan American World Airways, which was the biggest user of the Stratocruiser. There were a variety of interior configurations in the Models 377-10-26, -28, -29, -30, -32 accommodating from 55 to 112 passengers or, if equipped as a 'sleeper', with 28 upper- and lower-berth units, plus five seats. The main cabin was in the upper lobe of the 'double-bubble' fuselage, with a luxury lounge or cocktail bar seating 14 on the lower deck, reached via a spiral staircase.

Of the total of 55 that were built, Pan Am was operating 27 at one period. Of these, 10 were given additional fuel capacity to make them suitable for transatlantic operations, and were known as Super Stratocruisers. At a later date the entire fleet was equipped with General Electric CH-10 turbochargers, enabling each engine to develop an additional 37.3kW. British Overseas Airways Corporation also acquired a fleet of 17: only six of these were original purchases from Boeing, the remainder acquired from other airlines. After just over nine years' service with BOAC, 10 were sold to Transocean Airlines in the USA during 1958. Of these, four were converted to 117-passenger high-density seating, the remainder each having an additional 12 seats added to their standard 63- and 84-seat layouts. Before Stratocruisers disappeared from service during 1963, a few had been modified to a cargo configuration, but by far the strangest conversion resulted from those airframes acquired by Aero Spacelines Inc. Under the designation 377-PG, this company built an oversize cargo aircraft which it named 'Pregnant Guppy' and subsequently built other examples, using both Model 367 and 377 airframes, under variations of the Guppy name.