The Martin Company produced the prototype XPB2M Mars based on their PBM Mariner patrol bomber, with flight tests between 1941 and 1943. The Mars was converted by the Navy into a transport aircraft designated the XPB2M-1R. Satisfied with the performance, twenty of the modified JRM-1 Mars were ordered. The first, named "Hawaii Mars", was delivered in June 1945, but the Navy scaled back their order at the end of World War II, buying only the five aircraft which were then on the production line. The five Mars were completed, and the last delivered in 1947.