The Boeing 377 Stratocruiser was the airliner version of the 367 Boeing Stratofreighter, which in turn was the transport version of B-50 Superfortress. It first flew on July 8, 1947. Despite serious design flaws and a marginal service record [1], the Stratocruiser was one of the great post-war propeller airliners. Extremely complex and expensive, only 56 were built. It continued in mainline service until 1960, by then it had been made obsolete by the coming of the 707 and other first generation jetliners. The 377 was the flagship of the Pan Am and BOAC fleets from delivery in 1949 until the arrival of the 707. Its spiral staircase, which led to a lower-deck lounge, inspired the one on the 747. It was one of the few airliners with a double-decker seating arrangement (another was the French Breguet Deux Ponts) until the 747, however some airlines had lower-level lounges on their L-1011 Tristar aircraft.**********This aircraft type suffered 13 hull-loss accidents between 1951 and 1970 with a total of 140 fatalities. The worst single accident occurred on April 29, 1952; separation of the number two engine and propeller from Pan Am Flight 202 caused it to crash in the jungle near Carolina, Brazil, killing all forty-one passengers and nine crew.**********In the 1960s, Aero Spacelines modified several Stratocruisers to make oversized transports dubbed "Guppys". The first of these was the Pregnant Guppy, followed by the Super Guppy, and finally the Mini Guppy.