Douglas DC-4: With 24 firm commercial orders, production of the DC-4 began in the spring of 1939. But before the first was completed, the start of World War II necessitated the DC-4's reconfiguration as a military transport under the Army Air Force designation of C-54. (The DC-4 was known in the Navy as the R5D.) The plane made its first flight on February 14, 1942, with 1,162 being built as transports. Between 1942 and 1945, DC-4s successfully completed 79,642 transoceanic flights in support of the war effort, with only three ditchings, one of which was a test. A single C-54, nicknamed Sacred Cow, was built as the first official presidential transport aircraft. After the war, many were converted to commercial airliners. In addition 79 new DC-4s were delivered to airline customers in 1946 and 1947. Military DC-4s gained fame as the principle transport used during the 1948-1949 Berlin Airlift.