The XPB2M-1 Prototype for the Martin Mars Flying Boat

The XPB2M-1 prototype for the Martin Mars flying boat sits on the ground at the Martin Aircraft Factory, Martin State Airport in Baltimore, Maryland ,in late 1942 with a Piper J-3 Cub parked on its right wing to convey its massive size. 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 are operational.

Source :
From the collection of the National Air and Space Museum Archives, HGC-1073
Smithsonian National Air and Space Museum
https://en.wikipedia.org/wiki/Martin_JRM_Mars
https://www.flickr.com/photos/airandspace/albums/72157715574200936