What was the C-69B Constellation designed for?

When the United States entered World War II, the Constellation that Lockheed was developing for TWA was transferred to the Army Air Forces as a military transport under the designation C-69. The original version was a troop transport, of which 22 examples were built; nearly all of them were later converted into L-049 airliners. On that basis, Lockheed and the military studied several derivatives with more specific missions.

The C-69A was a proposed long-range troop transport. The C-69B shared that same approach, but was designed for a very specific task: carrying engines for the B-29 Superfortress to China. The relationship between the two aircraft was close, since the Wright R-3350 radial engine that powered the Constellation had been developed precisely for the B-29, and the pilot who flew the XC-69 prototype's first flight, Edmund Allen, was that bomber's test pilot at Boeing. In Lockheed's internal numbering, the C-69B was given the designation L-349.

No C-69B was ever manufactured, nor was the C-69D, another proposal, in this case for a VIP transport. A single C-69C-1 was built, a VIP aircraft with the internal designation L-549 that was later renamed ZC-69C-1, and the XC-69 prototype was converted into the XC-69E, an engine test bed with four Pratt & Whitney R-2800s. As the end of the war approached, the C-69 lost relevance to the war effort, and the program was redirected toward the airlines, where the Constellation would find its true calling.