The Lockheed Constellation is a four-engine long-range airliner with pressurized cabin for up to 81 passengers produced by the US-American manufacturer Lockheed Corporation. The military transport variant of the US Army Air Force operated during WWII was the C-69. The military transport variant of the L-749 operated by the US Air Force was designated C-121A.

The first variant of which 15 aircraft had been built was the military transport aircraft Lockheed C-69 with a capacity of 43 fully equipped troops.
The L-049 (73 built aircraft) was the first commercial variant, powered by four Wright Cyclone 745C-18BA-3 with 2200 hp / 1641 kW and a MTOW of 86250 lbs / 39122 kg.
The L-649 (14 built aircraft) was the first variant to be powered by the Wright Cyclone 749C-18BD-1, it has a MTOW of 94000 lbs / 42638 kg.
The L-749 has a MTOW of 102000 lbs / 46266 kg, the improved L-749A 107000 lbs / 48534 kg.