In the late 1950s, the Sukhoi Design Bureau, already an established fighter maker, started work on a successor to its Su-9 and Su-11 single-engined interceptors for the national Air defense Force. Similar to its predecessors, the new aircraft designated Su-15 had delta wings; unlike the Su-9/Su-11, however, it had twin engines and lateral air intakes freeing up the nose for a powerful fire control radar. First flown in May 1962, the Su-15 officially...