Subsonic
The first generation of jet fighters comprises the initial, subsonic jet fighter designs introduced late in World War II and in the early post-war period. They differed little from their piston-engined counterparts in appearance, and many employed unswept wings. Guns remained the principal armament. The impetus for the development of turbojet-powered aircraft was to obtain a decisive advantage in maximum speed. Top speeds for fighters rose steadily throughout World War II as more powerful piston engines were developed, and had begun approaching the transonic flight regime where the efficiency of piston-driven propellers drops off considerably.
F-86 Sabres in Pakistani markings
The first jets were developed during World War II and saw combat in the last two years of the war. Messerschmitt developed the first operational jet fighter, the Me 262. It was considerably faster than contemporary piston-driven aircraft, and in the hands of a competent pilot, was quite difficult for Allied pilots to defeat. The design was never deployed in numbers sufficient to stop the Allied air campaign, and a combination of fuel shortages, pilot losses, and technical difficulties with the engines kept the number of sorties low. Nevertheless, the Me 262 indicated the obsolescence of piston-driven aircraft. Spurred by reports of the German jets, Britain's Gloster Meteor entered production soon after and the two entered service around the same time in 1944. Meteors were commonly used to intercept the V-1 "buzz bomb", as they were faster than available piston-engined fighters. By the end of the war almost all work on piston-powered fighters had ended. A few designs combining piston and jet engines for propulsion – such as the Ryan FR Fireball – saw brief use, but by the end of the 1940s virtually all new combat aircraft were jet-powered.
Despite their advantages, the early jet fighters were far from perfect, particularly in the opening years of the generation. Their operational lifespans, especially for their gas turbine powerplants, could be measured primarily in hours; the engines themselves were fragile and bulky, and power could be adjusted only slowly. Many squadrons of piston-engined fighters were retained until the early-to-mid 1950s, even in the air forces of the major powers (though the types retained were the best of the World War II designs). Innovations including ejector seats and all-moving tailplanes were introduced in this period.
The Americans were one of the first to begin using jet fighters post-war. The Lockheed P-80 Shooting Star (soon re-designated F-80) was less elegant than the swept-wing Me 262, but had a cruise speed (660 km/h [410 mph]) as high as the combat maximum of many piston-engined fighters. The British designed several new jets, including the iconic de Havilland Vampire which was sold to the air forces of many nations.
The British transferred the technology of the Rolls-Royce Nene jet engine to the Soviets, who soon put it to use in their advanced Mikoyan-Gurevich MiG-15 fighters which were the first to introduce swept wings in combat, an innovation first proposed by German research which allowed flying much closer to the speed of sound than straight-winged designs such as the F-80. Their top speed of 1,075 km/h (668 mph) proved quite a shock to the American F-80 pilots who encountered them over Korea, along with their armament of two 23 mm cannons and a single 37 mm cannon compared to machine guns. Nevertheless, in the first jet-versus-jet dogfight in history, which occurred during the Korean War on 8 November 1950, an F-80 (as the P-80 had been redesignated) intercepted two North Korean MiG-15s near the Yalu River and shot them down.