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The Lockheed R6V Constitution was a large, propeller-driven, double-decker transport aircraft developed in the 1940s by Lockheed as a long-range, high-capacity transport and airliner for the U.S. Navy and Pan American Airways. Only two of the aircraft were ever built, both prototypes. Although these two planes went into service with the Navy, the Constitution design ultimately proved underpowered and too large for practical airline use at the time. Although the Martin JRM Mars flying boat had a slightly longer wingspan, the Constitution remains the largest fixed-wing aircraft type ever operated by the U.S. Navy.


The Lockheed Constitution began life in 1942 as a joint study by the U.S. Navy, Pan Am, and Lockheed. The design requirements, initially designated Lockheed Model 89, called for a large transport aircraft to improve upon the Navy's fleet of flying boats. Pan Am was involved in the study because such an aircraft had potential use as a commercial airliner. This transport would carry 17,500 lb (7,900 kg) pounds of cargo 5,000 miles (8,000 km) at a cruising altitude of 25,000 feet (7,600 m) and a speed greater than 250 mph (400 km/h). The aircraft would be fully pressurized and large enough so that most major components could be accessed and possibly repaired in flight. For instance, tunnels led through the thick wings to all four engines.

The aircraft was designed by a team of engineers led by Willis Hawkins and W.A. Pulver of Lockheed and Commander E. L. Simpson, Jr. of the Navy. The name Constitution was given to the project by Lockheed president Robert E. Gross.

The Constitution design had a "double bubble" fuselage, the cross section of which was a "figure eight". This unorthodox design, originally created in 1937 Curtiss-Wright's chief aircraft designer George A. Page Jr. and first introduced with the Curtiss C-46 Commando, utilized the structural advantages of a cylinder for cabin pressurization, without the wasted space that would result from a single large cylinder of the same volume.

The original contract from the Bureau of Aeronautics called for 50 Constitutions for a total price tag of $111,250,000. On VJ Day, however, the contract was scaled back to $27,000,000 for only two aircraft.