In the 1960s, work was carried out in the USSR to improve the flight characteristics of the Su-7. Many of this aircraft’s problems, such as long takeoff and landing runs resulting from high liftoff and touchdown speeds and poor manoeuvrability, could be solved by variable-geometry wings. In 1965, an aircraft was developed based largely on the Su-7 design, with variable-geometry wings. It was first flown in 1966 and entered production in 1967 under the designation Su-17.
It was equipped with a new radio navigation and aiming system, but the fuel-thirsty AL-7 engine and the associated short range remained a problem. The Su-17 was produced until 1975. In 1972, production of the improved Su-17M began, powered by the modern AL-21 engine. The aircraft had increased fuel capacity, a modified fuselage structure, an improved wing geometry change mechanism, weapons load increased to 4,000 kg and could carry guided missiles. Production continued until 1976. In 1972, an export version was also developed, designated Su-20, capable of carrying R-3S and R-13M air-to-air missiles.
Poland, as the only Warsaw Pact country, purchased 26 Su-20 aircraft, delivered between 1974 and 1977. They were operated until 1997 by the 7th Bomber-Reconnaissance Aviation Regiment at Powidz. The Su-20s were the first variable-geometry wing aircraft in Polish aviation. Some examples, unofficially called Su-20R, had a camera permanently installed in the lower part of the fuselage behind the nose wheel bay. The successor to the Su-20 was the Su-22, still operated today by the Polish Air Force. In NATO code, the Su-20 bore the designation Fitter C.
| Wingspan | (max. wing sweep) 10.03 m |
| Length | (with pitot tube) 18.73 m |
| Takeoff weight | (maximum) 18120 kg |
| Maximum speed | (clean) 2230 km/h |
| Ceiling | 15200 m |
| Range | 2500 km |
| Armament | 2 NR-30 cannons, 30 mm cal., missiles and bombs up to 4000 kg |
| Engine | AL-21 F3 with 11200 kG thrust |
