A contemporary of the Hawker Hurricane and Messerschmitt Bf 109, the P-35 was the first single-seat fighter in United States Army Air Corps to feature all-metal construction, retractable landing gear, and an enclosed cockpit.

The SEV-3 first flew in June 1933 and was developed into the Seversky BT-8 basic trainer, 30 of which were ordered by the United States Army Air Corps (USAAC) in 1935.

The SEV-1XP was re-engined again, with a two-row Pratt & Whitney R-1830-9 "Twin Wasp" replacing the Cyclone and a modified vertical stabilizer fitted, becoming the SEV-7.

While more expensive than the Curtiss and Vought designs, the Seversky was a clear winner of the Air Corps' competition, with an order for 77 P-35 fighters and spare parts equivalent to eight airplanes being placed on 16 June 1936 at a cost of $1,636,250.

[9][10] Modifications from SEV-1XP to production P-35 standard included partial instead of complete mainwheel fairings and seven degrees of dihedral to the outer wing panels.

[12] When it wanted further fighters in 1937, the Air Corps, who were unhappy with both the slow delivery of the P-35, and sale of 2PA two-seat aircraft to the Japanese Navy, ordered 210 Curtiss P-36s.

[14] Seversky continued to develop the design with the hope of selling more aircraft both to the Air Corps and to civil and export customers.

Another civil aircraft was the DS, (or Doolittle Special), a single seater for James Doolittle, employed at the time by the Shell Oil Company, while the AP-7 was another racer, powered by a 1,200 hp (895 kW) R-1830 engine and used by Jacqueline Cochran to win the 1938 Bendix Trophy race and to set a women's air speed record.

One was the XP-41 (which had the company designation AP-4D, which was a P-35 with a 1,200 hp (895 kW) R-1830-9 engine fitted with a two-stage supercharger) and the AP-4, which had a turbo-supercharger mounted in the belly of a deeper fuselage.

Sweden ordered 52 2PAs (Swedish designation B 6), able to carry 1,350 lb (612 kg) of bombs, but received only two prior to the U.S. embargo directed to combatants.

The aircraft used a wet wing to save weight and ground personnel quickly learned about the persistent fuel leaks.

The P-35's performance was poor even by contemporary standards and, although USAAC aviators appreciated the aircraft's ruggedness, it was already obsolete by the time deliveries were finished in 1938.

In October 1941, the P-35s were earmarked for transfer to the Philippine Army Air Corps after sufficient Curtiss P-40 Warhawks were received by the FEAF.

Ramon Zosa of the PAAC on 30 April, and flew its last sortie out of Del Monte Airfield, accompanying a P-40 on a strafing attack of Japanese landings at Macajalar Bay on 3 May 1942.

The aircraft were operated alongside other units assigned to the Svea Air Force Wing (F 8) protecting Stockholm, replacing the obsolete Gloster Gladiators.

Later, 10 aircraft were equipped with cameras but retained their J 9 fighter designation and, in addition, a number of others were used for liaison and general flight training.