Development

The first generation of MiG jet fighters was based on designs similar to late-WWII German jet designs, starting with the subsonic MiG-15, MiG-17, and the low supersonic swept-wing MiG-19. A number of experimental Mach 2 Soviet designs were based on nose intakes with either swept-back wings, such as the Sukhoi Su-7, or tailed delta wings, of which the MiG-21 would be the most successful.

The E-5 prototype of the MiG-21 was first flown in 1955 and made its first public appearance during the Soviet Aviation Day display at Moscow's Tushino Airport in June 1956. The first delta-wing prototype, named "Ye-4", (also written as "E-4") flew on 14 June 1956, and the production MiG-21 entered service in early 1959. Employing a delta-wing configuration, the MiG-21 was the first successful Soviet aircraft combining fighter and interceptor characteristics in a single aircraft. It was a lightweight fighter, achieving Mach 2 speed using a relatively low-powered afterburning turbojet, and is thus comparable to the American F-104 Starfighter and French Dassault Mirage III.

When the MiG-21 was first introduced, it exhibited several flaws. Its early version air-to-air missiles, the Vympel K-13 (NATO reporting name AA-2 'Atoll'), were not successful in combat, and its gyro gunsight was easily thrown off in high-speed maneuvers, making the initial version of the MiG-21 an ineffective aircraft. These problems were remedied, and during the Middle Eastern and Vietnam wars, the MiG-21 proved to be an effective aircraft. Subsequent MiG-21 models added design modifications to incorporate lessons learned in these wars.

Like many aircraft designed as interceptors, the MiG-21 had a short range. This was not helped by a design defect where the center of gravity shifted rearwards once two-thirds of the fuel had been used. This had the effect of making the plane uncontrollable, resulting in an endurance of only 45 minutes in clean condition. The delta wing, while excellent for a fast-climbing interceptor, did mean that any form of turning combat led to a rapid loss of speed. However, the light loading of the aircraft could mean that, at 50% fuel and with 2 AA-2 'Atoll' air-to-air missiles, a climb rate of 58,000 ft (17,670 m) per minute was possible, not far short of the performance of the later F-16A. Given a skilled pilot and capable missiles, it could give a good account of itself against contemporary fighters. It was replaced by the newer variable-geometry MiG-23 and MiG-27 'Flogger' for ground support duties. However, not until the MiG-29 'Fulcrum' would the Soviet Union ultimately replace the MiG-21 as a maneuvering dogfighter to counter new American air superiority types.

The MiG-21 was exported widely and continues to be used well past the time where it might have been considered obsolete. The aircraft's simple controls, engine, weapons, and avionics were typical of Soviet-era military designs. While technologically inferior to the more advanced fighters it often faced, low production and maintenance costs made it a favorite of nations buying Eastern Bloc military hardware.

Due to the lack of available information, early details of the MiG-21 were often confused with those of the similar Sukhoi fighters also under development. Jane's All the World's Aircraft 1960-1961 describes the "Fishbed" as a Sukhoi design, and uses an illustration of the Su-9 'Fishpot'.