Douglas built 1,241 of the DC-4s and its military counterparts, the C-54 Skymaster for the Army Air Forces and the R5D for the Navy. During the war, C-54s flew a million miles a month over the rugged North Atlantic -- more than 20 round trips a day. A special VC-54C, nicknamed the "Sacred Cow" by the White House press corps, became the first presidential aircraft, ordered for Franklin D. Roosevelt. In the years immediately following the war, new DC-4s and used C-54s carried more passengers than any other four-engine transport.