The airplane made its maiden flight on 20 January 1934 and was flown to Wright Field for Army testing under the experimental military designation XP-940 five days later. During testing, the XP-940 achieved a maximum speed of 220 mph at 10,000 ft (354 km/h at 3,050 m). After testing, the XP-940 was returned to the factory in March for modifications. Due to the tight-fitting canopy and restricted pilot vision from the cockpit enclosure, Boeing reverted to an open cockpit design, retaining the long headrest all the way to the tail. The engine was replaced by a 600 hp (450 kW) R-1340-35 with a drag ring, similar to the P-26A's. It was also fitted with flaps, which the XP-940 lacked.