Lockheed Model 44 Excalibur

The Lockheed Model 44 Excalibur was a proposed American airliner designed by Lockheed in the late 1930s, and it was never built. It was the company's first four-engined design, a low-wing monoplane with retractable tricycle landing gear that began with twin tail fins and ended with three. Lockheed announced the Model 44 in April 1939, when American manufacturers were racing to build airliners that could carry more passengers farther than the Douglas DC-3 generation. The first plan called for 21 passengers, later revised to 36, with four radial engines of the Pratt and Whitney Twin Wasp or Wright Cyclone families, and a request from Pan American Airways influenced both the revision and the added third fin. A 40-passenger variant, the L-144, was planned but cancelled even though South African Airways had placed a potential order for two. Lockheed built a full-scale mockup, and Pan American was close to ordering when Howard Hughes, who had gained ownership of Transcontinental and Western Air, funded a much faster and longer-range redesign with Wright R-2600 engines. That design became the Model 49, Lockheed dropped the Excalibur name, and the end result was the Constellation.