The Martin YO-45 was a temporary designation given to a Martin YB-10 while it was being evaluated as a high speed reconnaissance aircraft.
When it first appeared the Martin B-10 was an advanced aircraft – a cantilever mid wing monoplane with enclosed cockpits, retractable landing gear and a three man crew, powered by two 600hp Wright SR-1820-E Cyclone engines.
The YO-45 was given two 675hp Wright R-1820-17 Cyclone engines, and evaluated for use as a high speed reconnaissance aircraft. This was at a time when the USAAF was struggling to decide what it wanted from its observation aircraft, with some arguing for three man fast light bombers on the grounds that they would be more survivable and others for much lighter, slow flying aircraft that would be able to loiter over the battlefield. Events in Europe in 1940 soon proved that the slow flying aircraft, most famously the Fieseler Storch, was what was needed, and aircraft like the YO-45 disappeared from the short range observation role.