The Boeing 377 Stratocruiser was the civilian version of the C-97 Stratofreighter, which in turn was derived from the B-50 Superfortress. It first flew on July 8, 1947. Despite serious design flaws and a marginal service record, the Stratocruiser was considered one of the greatest post-war propeller airliners.  In the 1960s, several Stratocruisers were modified by Aero Spacelines to make oversized transports and were dubbed as "Guppys".

The Boeing 377 has a seating capacity of up to 100 passengers on main deck and an additional 14 in lower deck lounge.  The typical seating for 63 or 84 passengers.  It incorporates 4 Pratt & Whitney R-4360-B6 Wasp Major 28-cylinder radial engines four-bladed propellers.  It has a maximum speed of 375 mph and a range of 3,650 nm.  The primary users and operators of the Boeing 377 are the Pan Am and the BOAC.  Extremely complex and expensive, only 56 were built. It continued in mainline service until 1960, when it had been made obsolete by the coming of the 707 and other first generation jetliners.