The MiG-31's N-007 Zaslon radar was the world's first phased-array unit; it can track 10 targets simultaneously, and control the engagement of four of them at once. Operational experience showed that the MiG-31 was deficient in range and some 40-45 aircraft were fitted with semi-retractable in-flight refueling probes.
Introduced in 1990, the MiG-31B gained an improved radar with better electronic counter measures capability, upgraded R-33S air-to-air missiles armament and improved avionics, including new digital processors. Existing MiG-31s were upgraded to the same standard as the MiG-31BS.MiG-31s continue to form the back bone of Russia's air defenses. At least 300 are in service, equipping around 15 fighter regiments. Kazakhstan is the only former Soviet republic to operate the MiG-31, with a regiment based at Semipalatinsk.
The MiG-31M remains the most advanced version of the Foxhound yet seen. It was designed to exploit the longer-range R-37 (with a claimed reach of up to 300 km) as well as the R-77 air-to-air missiles. It featured Zaslon-M radar, plus a range of new avionics systems, an extensively redesigned rear cockpit with new displays and uprated D-30F-6M engines. The first of seven flying MiG-31M prototypes made its maiden flight in 1985. The MiG-31M had the misfortune of being born at the wrong time, when defense budgets were being slashed. Today, the programme seems to be dead in the water. MiG MAP has proposed several MiG-31 variants for a variety of roles including defense suppression and long-range interdiction, as well as an export MiG-31E interceptor with downgraded radar.The latest version is the MiG-31BM; this is billed as a true multi-role Foxhound, able to undertake long-range interception, precision strike and defense suppression tasks. Both cockpits feature advanced displays allowing the crew to deploy precision-guided munitions.