with ballast in the nose instead of radars, flat fuselage undersurface (i.e. no recessed weapon system bays) and had large winglets above and below the wing-tips. Equipped with Vympel ASAT missiles. Two prototypes were built. MiG-31LL Special modification used as a flying laboratory for testing of ejection seats during flight. MiG-31 01DZ Two-seat all weather, all altitude interceptor. Designated as MiG-31 01DZ when fitted with air-to-air refueling probe. One hundred produced of DZ variant. MiG-31B Second production batch with upgraded avionics and in-flight refueling probe introduced in 1990. Its development was the result of the Soviet discovery that Phazotron radar division engineer Adolf Tolkachev had sold information on advanced radars to the West. A new version of the compromised radar was hastily developed. MiG-31B also have the improved ECM and EW equipment with integration of improved R-33S missiles. Long range navigation system compatible with Loran/Omega and Chaka ground stations added. This model replaced the 01DZ models in late 1990. MiG-31E Export version of the MiG-31B with simplified avionics. Never entered in serial production. MiG-31BS Designation applied to type 01DZ when converted to MiG-31B standard. MiG-31BM After passing state testing in 2008 this modernized variant of MiG-31B was approved for introduction into air force of Russia. 50 planes are modified to MiG-31BM (Bolshaya Modernizatsiya/Big Modernization) standard in accordance with 2011 contract. Efficiency of modernized MiG-31BM is 2.6 times greater than basic MiG-31. The MiG-31BМ's maximum detection range for air targets was increased in the upgrade to . It had the ability to automatically track up to ten targets, and the latest units can track up to 24 targets and simultaneously engage up to eight targets. The on-board Argon-K is replaced with new Baget 55-06 computer that selects four targets of highest priority, which simultaneously are engaged by long-range R-33S air-to-air missiles. New long range missile R-37 (missile) with speed of Mach 6 and range up to is developed during modernization process for use with newly modernized MiG-31. MiG-31BM has multi-role capability as is capable of using anti-radar, air to ship and air to ground missiles. It has some of avionics unified with MiG-29SMT and has refueling probe. MiG-31BM broke world record while spending seven hours and four minutes in the air while covering the distance of . MiG-31BSM An upgrade of the BS version, it is the latest modernization variant first time contracted in 2014 for modernization of 60 aircraft, it