Like the Boeing XB-15, the Martin XB-16 (Martin Model 145) was designed to meet the United States Army Air Corps' request for a bomber that could carry 2,500 lb (1,100 kg) of bombs 5,000 mi (8,000 km).
The XB-16 was to use four Allison V-1710 liquid-cooled inline engines; contemporary American aircraft used air-cooled radial engines.
In 1935, Martin revised the XB-16 design. The wing span was increased from 140 ft (42.7 m) to 173 ft (52.7 m), and a set of V-1710 engines added to the trailing edge. This version had a wingspan 20% greater than that of the B-29 Superfortress, the first operational bomber that would fill the role intended for the XB-16.
The XB-16 was cancelled for essentially the same reason the B-15 project was: it wasn't fast enough to meet the requirements set by the Army. Since both were cancelled around the same time, Martin did not have time to produce an XB-16.