Rumors that the Soviet Union had produced a swept-wing fighter had circulated a year before the Mikoyan-Gurevich MiG-15 first appeared at air shows in 1949.
Despite the level of activity taking place with swept-wing aircraft, the Navy was not initially focused on the development of such aircraft.
This was largely because the Navy's focus at the time was defending the battle group against high speed, high altitude bombers with interceptors, as well as escorting medium-range carrier-based bombers in all weather conditions.
Air-to-air combat was of less interest.
 Nonetheless, the Navy appreciated the importance of getting a capable carrier-based swept-wing jet fighter.
Grumman was awarded a contract for the development of a swept-wing fighter jet in 1951.
The arrival of the MiG-15, which easily outclassed straight-wing fighters in the air war over North Korea was a major factor.

Prototypes were quickly produced by modifying Panthers, and the first (XF9F-6) flew on 20 September 1951.
The aircraft was still subsonic, but the critical Mach number was increased from 0.79 to 0.86 at sea level and to 0.895 at 35,000 ft (10,000 m), improving performance markedly over the Panther.
Instead of using conventional ailerons for roll control, the F9F-6 uses spoilers  on the upper surfaces of the wing.
Wing fences were soon added and the spoilers extended from the fences to the tips of the wing.
The rudder pedals controlled the part of the rudder below the horizontal tail surface, while the upper portion of the rudder was controlled by a yaw damper.
This allowed the Cougar to fly safely and easily without the upper portion of the tail.
Rumors that the Soviet Union had produced a swept-wing fighter had circulated a year before the Mikoyan-Gurevich MiG-15 first appeared at air shows in 1949. Despite the level of activity taking place with swept-wing aircraft, the Navy was not initially focused on the development of such aircraft. This was largely because the Navy's focus at the time was defending the battle group against high speed, high altitude bombers with interceptors, as well as escorting medium-range carrier-based bombers in all weather conditions. Air-to-air combat was of less interest.  Nonetheless, the Navy appreciated the importance of getting a capable carrier-based swept-wing jet fighter. Grumman was awarded a contract for the development of a swept-wing fighter jet in 1951. The arrival of the MiG-15, which easily outclassed straight-wing fighters in the air war over North Korea was a major factor.
Prototypes were quickly produced by modifying Panthers, and the first (XF9F-6) flew on 20 September 1951. The aircraft was still subsonic, but the critical Mach number was increased from 0.79 to 0.86 at sea level and to 0.895 at 35,000 ft (10,000 m), improving performance markedly over the Panther. Instead of using conventional ailerons for roll control, the F9F-6 uses spoilers  on the upper surfaces of the wing. Wing fences were soon added and the spoilers extended from the fences to the tips of the wing. The rudder pedals controlled the part of the rudder below the horizontal tail surface, while the upper portion of the rudder was controlled by a yaw damper. This allowed the Cougar to fly safely and easily without the upper portion of the tail.
Grumman F-9 Cougar