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