The Martin JRM Mars is a large, four-engined cargo transport flying boat designed and built by the Martin Company for the United States Navy during World War II. It was the largest Allied flying boat to enter production, although only seven were built. The United States Navy contracted the development of the XPB2M-1 Mars in 1938 as a long-range ocean patrol flying boat, which later entered production as the JRM Mars long-range transport. Four of the surviving aircraft were later converted for civilian use to firefighting water bombers. Two of the aircraft still remain based at Sproat Lake just outside of Port Alberni, British Columbia, although neither is operational. Design and development The Glenn L. Martin Company scaled up their PBM Mariner patrol bomber design to produce the prototype XPB2M-1 Mars. The XPB2M-1 was announced on 8 November 1941. Delayed by an engine fire during ground runs, the aircraft first flew on 23 June 1942. After flight tests with the XPB2M between 1942 and 1943, she was passed on to the Navy. The original patrol bomber concept was considered obsolete by this time, and the Mars was converted into a transport aircraft designated the XPB2M-1R. The Navy was satisfied with the performance and ordered 20 of the modified JRM-1 Mars. The first, named Hawaii Mars, was delivered in June 1945, but with the end of World War II the Navy scaled back their order, buying only the five aircraft which were then on the production line. Though the original Hawaii Mars was lost in an accident on the Chesapeake Bay a few weeks after it first flew, the other five Mars were completed, and the last delivered in 1947. Operational history U.S. Navy service Named the Marianas Mars, Philippine Mars, Marshall Mars, Caroline Mars, and a second Hawaii Mars, the five production Mars aircraft entered service ferrying cargo to Hawaii and the Pacific Islands on 23 January 1944. The last production airplane (the Caroline Mars) was designated JRM-2, powered by Pratt & Whitney R-4360 engines, and featured a higher maximum weight and other improvements. On 4 March 1949, the Caroline Mars set a new world passenger load record by carrying 269 people from San Diego to San Francisco, CA. On 5 April 1950, the Marshall Mars was lost near Hawaii when an engine fire consumed the airplane after her crew had evacuated. The remaining "Big Four" flew record amounts of