Two Piper Cubs were put on the wing of the Martin XPB2M-1 Mars prototype to show its size. This doesn't work too well in this view. The flying boat was rolled out on 27 September 1941. The photo date is given as late 1942, which seems too late. The Cubs, NC40743 and NC40745, are listed as manufactured in 1941. Photo by: Hans Groenhoff / Smithsonian Institution

Martin Mars prototype at the Martin factory, repaired following the #3 engine fire on 5 December 1941, but still before its first flight. It is seen here still in its original configuration as a patrol bomber, complete with gun turrets and provisions for bombing. However, the aircraft was soon to be converted to XPB2M-1R transport aircraft, which involved removing all armament and armored plating, and adding extra cargo hatches, cargo loading equipment and reinforcing the decking. Photo from: US Navy - National Naval Aviation Museum

The Martin Mars prototype in take-off at an unknown location, possibly the Pacific off San Francisco. This photo was taken circa 1944, about two years after it had been converted from patrol bomber to transport aircraft, by the removal of its gun turrets, bomb bays, armored plating and other combat provisions. Instead, this transport version received additional cargo hatches and cargo loading equipment, as well as reinforced decking. Photo from: US Navy - National Naval Aviation Museum