Fighter aircraft
1940s–1950s: First-generation

The first generation of jet fighters comprised the initial, subsonic jet-fighter designs introduced late in World War II (1939–1945) and in the early post-war period. They differed little from their piston-engined counterparts in appearance, and many employed unswept wings. Guns and cannon remained the principal armament. The need to obtain a decisive advantage in maximum speed pushed the development of turbojet-powered aircraft forward. Top speeds for fighters rose steadily throughout World War II as more powerful piston engines developed, and they approached transonic flight-speeds where the efficiency of propellers drops off, making further speed increases nearly impossible.

The first jets 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 A, primarily serving with the Luftwaffe's JG 7, the world's first jet-fighter wing. It was considerably faster than contemporary piston-driven aircraft, and in the hands of a competent pilot, proved quite difficult for Allied pilots to defeat. The Luftwaffe never deployed the design 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 commonly served to intercept the V-1 flying bomb, as they were faster than available piston-engined fighters at the low altitudes used by the flying bombs. Nearer the end of World War II, the first military jet-powered light-fighter design, the Luftwaffe intended the Heinkel He 162 A Spatz (sparrow) to serve as a simple jet fighter for German home defense, with a few examples seeing squadron service with JG 1 by April 1945. 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 fighters were jet-powered.

Despite their advantages, the early jet-fighters were far from perfect. The operational lifespan of turbines were very short and engines were temperamental, while power could be adjusted only slowly and acceleration was poor (even if top speed was higher) compared to the final generation of piston fighters. Many squadrons of piston-engined fighters remained in service 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 ejection seats, air brakes and all-moving tailplanes became widespread in this period.

The Americans began using jet fighters operationally after World War II, the wartime Bell P-59 having proven a failure. The Lockheed P-80 Shooting Star (soon re-designated F-80) was more prone to wave drag than the swept-wing Me 262, but had a cruise speed (660 km/h (410 mph)) as high as the maximum speed attainable by many piston-engined fighters. The British designed several new jets, including the distinctive single-engined twin boom de Havilland Vampire which Britain 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 fighter, which used fully swept wings that allowed flying closer to the speed of sound than straight-winged designs such as the F-80. The MiG-15s' top speed of 1,075 km/h (668 mph) proved quite a shock to the American F-80 pilots who encountered them in the Korean War, along with their armament of two 23 mm (0.91 in) cannons and a single 37 mm (1.5 in) cannon. Nevertheless, in the first jet-versus-jet dogfight, which occurred during the Korean War on 8 November 1950, an F-80 shot down two North Korean MiG-15s.

The Americans responded by rushing their own swept-wing fighter – the North American F-86 Sabre – into battle against the MiGs, which had similar transsonic performance. The two aircraft had different strengths and weaknesses, but were similar enough that victory could go either way. While the Sabres focused primarily on downing MiGs and scored favorably against those flown by the poorly-trained North Koreans, the MiGs in turn decimated US bomber formations and forced the withdrawal of numerous American types from operational service.

The world's navies also transitioned to jets during this period, despite the need for catapult-launching of the new aircraft. The U.S. Navy adopted the Grumman F9F Panther as their primary jet fighter in the Korean War period, and it was one of the first jet fighters to employ an afterburner. The de Havilland Sea Vampire became the Royal Navy's first jet fighter. Radar was used on specialized night-fighters such as the Douglas F3D Skyknight, which also downed MiGs over Korea, and later fitted to the McDonnell F2H Banshee and swept-wing Vought F7U Cutlass and McDonnell F3H Demon as all-weather / night fighters. Early versions of Infra-red (IR) air-to-air missiles (AAMs) such as the AIM-9 Sidewinder and radar-guided missiles such as the AIM-7 Sparrow whose descendants remain in use as of 2021, were first introduced on swept-wing subsonic Demon and Cutlass naval fighters.
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