When the Sukhoi bureau was re-established in 1953 it hedged its bets, developing two families of prototype in parallel: a swept-wing series (the “S” aircraft) and a tailed-delta series (the “T” aircraft). The swept wing became the Su-7 ground-attack aircraft; the delta became the interceptor. The delta’s big wing gave the lift needed to reach and hold high altitude, while the all-moving tailplane preserved control at supersonic speed — a combination that suited the PVO’s need for a fast-climbing, high-flying missile carrier more than it suited close-in dogfighting.

The result reached the PVO as the Su-9 in 1959, and the design was refined into the Su-11 a few years later. Both shared the same basic tailed-delta airframe and single-engine layout; the visible differences were in the nose — a longer radome on the Su-11 — and in the missiles they carried.

The Su-9 entered service armed only with four RS-2US missiles — a beam-riding weapon derived from the K-5 family. Beam-riding meant the missile flew along the interceptor’s radar beam toward the target, so the pilot had to hold the enemy steadily in the radar’s cone throughout the engagement. It worked best against large, non-manoeuvring targets such as bombers at altitude, which was exactly the threat the PVO expected. The Su-11 replaced these with the heavier, longer-ranged R-8, but the philosophy stayed the same: a radar-directed missile interceptor rather than a gun fighter.

The performance that made the Fishpot a good high-altitude interceptor also made it a handful. The delta wing bled energy quickly in hard manoeuvres, endurance was limited, and the landing approach was fast — a challenge on the shorter runways of the era. Range was modest, so the type depended heavily on ground-controlled interception to be vectored efficiently onto its target. These limitations, together with the single engine, were among the reasons the PVO moved on to the twin-engined Su-15 and the MiG-25.

The Su-9 and Su-11 were Soviet state products, built for the PVO and never sold on an open market, so no firm flyaway unit price or cost-per-flight-hour figure exists in the public record. Any precise dollar figure attached to these types should be treated as an estimate rather than a sourced number. What can be said with confidence is that the Su-11 was built in far smaller numbers (~108) than the Su-9 (well over a thousand), and that both were superseded by more capable — and more expensive — twin-engined interceptors.