09/30/2014. Remarks by Johan Visschedijk: "The US Navy's largest flying boat was ordered on August 23, 1938, as the experimental patrol bomber XPB2M-1. The Mars was first flown on July 3, 1942, subsequently it was modified to a transport configuration as XPB2M-1R in December 1943. Twenty JRM-1 transports, with single in place of twin tail and other changes, were ordered in January 1945 (BuNo 76819 to 76838), but only five were built, plus one JRM-2 with higher weight. The JRM-1s were modified to the latter standard as JRM-3s and they were operated by VR-2 based at Alameda, California, USA. The Mars had four 2,300 hp Wright R-3350-8 engines."