In 1947 U.S. Army Air Forces officials ordered the 29th production DC-6 to be modified as a replacement for the aging VC-54C Sacred Cow presidential aircraft. Different from the standard DC-6 configuration, The Independence included an aft stateroom for the president and a main cabin which seated 24 passengers or 12 “sleeper” berths. Other improvements included reversible-pitch propellers, weather radar, a radar altimeter, autopilot and other advanced navigation equipment. Water injection gave the engines more power at takeoff, and larger fuel tanks enabled it to fly nonstop to any location within the continental United States.