The XB-10 had full NACA cowlings to decrease drag, a pair of 675 hp Wright R-1820-19 engines, an 8-foot increase in the wingspan from the test version, canopies for the 3-man crew, and an enclosed nose turret. When the XB-10 flew during trials in June, it recorded a speed of 197 mph at 6,000 ft—impressive performance for 1932. The Army ordered 48 B-10s on 17 January 1933. The first 14 aircraft were designated YB-10 and delivered to Wright Field in November 1933. These early models were used near the end of the Army Air Corps Mail Operation in early 1934 and again during the 1934 AAC “Alaska Flight” commanded by Lt Col Hap Arnold.