In 1935 the US Army Air Corps initiated a series of design competitions aimed at procuring an advanced monoplane fighter. At an earlier date, however, the Seversky Aircraft Corporation had begun the design of a two-seat aircraft in this category as a private venture, completing its construction in early 1935. This, which had the company designation SEV-2XP, was submitted for competition, but while being flown to Wright Field on 18 June 1935 to participate, was involved in an accident which caused sufficient damage to necessitate its return to the factory for repair. Designed by Alexander Kartyeli who, a little later, was to head design of the famous P-47 Thunderbolt, the SEV-2XP had fixed landing gear. During the repair process Kartveli had designed retractable main and tailwheel units which could be adapted to the original airframe without major structural change and, at the same time, changed the accommodation to provide only a single seat. The powerplant comprised an 850 hp (634 kW) Wright R-1820-65 Cyclone 9, and with the changes which had been made the company were confident of attaining a maximum speed in excess of 300 mph (483 km/h).

In this form the redesignated SEV-1XP was delivered to Wright Field in mid-August 1935, but failing to achieve the desired performance was taken back to the Seversky plant where a Pratt & Whitney R-1830-9 Twin Wasp engine was installed. Theoretically of the same rating as the Cyclone which it had displaced, it was found during testing that the SEV-7 (as it was then designated) had suffered a decline in performance. Finally, under the designation AP-1 and with an R-1830-9 engine which was rated officially at 950 hp (708 kW), the USAAC ordered 77 of this version as the P-35. With a low-set elliptical wing that was very similar in planform to that of the Supermarine Spitfire, these fighters were armed with one 0.50-in (12.7-mm) and one 0.30-in (7.62-mm) synchronised machine-gun mounted in the close-fitting engine cowling.

P-35s began to enter service in July 1937, with 76 of them being delivered by August 1938. The last of the production batch was completed in changed form, with airframe modifications and the installation of a 1,200- hp (895-kW) Pratt & Whitney R-1830-19 engine with two-stage supercharger, and this was designated XP-41.

In 1939 Seversky adopted the name Republic Aviation Corporation, and in June received an order from the Swedish government for 15 of the P-35s which, in export form, were identified as EP-1s. This version differed from the USAAC's P-35s in having a more powerful Twin Wasp engine and two additional machine-guns. The initial order, and a following order for 45 more examples, had been completed by mid- June 1940, but the 60 machines which comprised the final order were requisitioned by the US government in October 1940. Allocated the designation P-35A, these had all been delivered by early February 1941, and during the year 48 were despatched to the Philippines where, equipping such units as the USAAC's 3rd, 17th and 20th Pursuit Squadrons, only eight remained serviceable after the first two days of the Japanese attacks on 7/8 December 1941. The 12 which remained in the US were subsequently supplied to Ecuador.

As a private venture, Seversky built the prototype of a two-seat fighter which it designated Seversky SEV-2XP, but while being evaluated by the US Army Air Corps in June 1935 this prototype was damaged sufficiently to need factory repair. The company's designer, Alexander Kartveli, took the opportunity to introduce retractable main landing gear and revised the cockpit as a single seater, the aircraft then being redesignated SEV-1XP. When tested by the USAAC it was found to be underpowered, its 850 hp (634 kW) Wright R-1820-GB Cyclone radial then being replaced by a Pratt & Whitney R-1830-9 Twin Wasp of similar output, resulting in the new designation SEV-7. Performance had deteriorated still further, the R-1830-9 delivering little more than 85 percent of its rated power, resulting in the installation of an R-1830-9 engine with a guaranteed output of 950 hp (708 kW) in the aircraft that was then redesignated AP-1. ln this form the type was ordered by the USAAC under the designation P-35, the first of 77 aircraft being delivered in July 1937. The last of the batch was completed as an improved aircraft designated XP-41, which flew shortly before the company changed its name to Republic Aircraft Corporation, and this was fundamentally the prototype of the Republic P-43 Lancer.

Under the designation EP-1 the type was offered for export, the Swedish government ordering the first 15 of a batch of 120 designated EP-106, which differed primarily by having a more powerful R-1830-45 engine and heavier armament. Half of these had been delivered by 18 June 1940, being designated J9 in Swedish service, but the balance of 60 was requisitioned for the USAAC and delivered under the designation P-35A. They were severely mauled by the Japanese when deployed in the Philippines, only eight of 48 remaining airworthy after the first two days of enemy attacks, and this represented the first and last operational use of the type. The remaining 12 P-35As were later supplied to Ecuador.

2PA-L: The Seversky corporation developed a two-seat fighter intended for export based on the design of the P-35. Designated 2PA-L, it was powered by a Wright R-1820 engine of 1000 hp (746 kW). The sole 2PA-L was sold to the Soviet Union in March of 1938. An amphibian two-seat fighter similar to the 2PA-L but powered by a 850 hp (634 kW) Wright R-1820-G2 engine was acquired by the Soviet Union in the same month, along with a license for its manufacture. In the event, the Soviet Union never took up the option for the manufacture of the 2PA-L.

FN-1: In 1937, Seversky entered a P-35 (designated FN-1) in a US Navy competition for a new carrier-based fighter to replace the Grumman biplanes then in service. It competed against the Grumman F4F and the Brewster F2A. It was powered by a 950 hp Wright R-1820-22 engine, and carried an arrestor hook and bomb racks. Visibility was improved by the fitting of a larger bulged windscreen. The top speed was only 267 mph (429 km/h), not much faster than that of the Grumman F3Fs that was intending to replace. In any case, the Brewster F2A won the competition.  

SPECIFICATIONS
Span: 36 ft.
Length: 25 ft. 4 in.
Height: 9 ft. 9 1/2 in.
Weight: 5,600 lbs. max.
Armament: One .50-cal. and one .30-cal. fuselage mounted machine gun plus 320 lbs. of bombs.
Engine: Pratt & Whitney R-1830 of 850 hp.
Crew: One
Cost: $22,500