The heaviest fighter / interceptor in the world, the Mig-31 is the same as the replacement of the Mig-25 'Foxbat', the prototype Ye-155MP took the first flight on 16 September 1975. As the heaviest fighter / Much heaver than other similar aircrafts.At the same time, tow powerful D-30-F6 engines and a strong air field gave it a top speed to Mach 2.8 at high-altitude and Mach 1.23 at low level.
The Mig-31B were put out of the threaten of the western countries in the 1980s, they can be served as the mixture of the Mig-31BS which developed from the basic Mig-31 sans suffixe and the Mig-31DZ, the IFR system testbed However, a series of new avionics and WCS made it much more efficient than any other version.
The lastest upgrade version of the Foxhound is the Mig-31BM, the new multi-role version which developed from the Mig-31B and the Mig-31BS. Program started from 1997.The new version Mig-31BM is no longer a interceptor only , The can carry a variety of air-to-surface weapons such as Kh-25, Kh-29, Kh-31, Kh-59 etc.