The Foxhound was developed to counter the American B-1 bomber. It is off of the MiG-25 Foxbat.
Despite never achieving the top speed of the MiG-25, the MiG-31 fixed many of the problems the Foxbat had. First, the Foxhound's airframe was strengthened to permit super-sonic flight at low altitudes. Second, the engines of the MiG-31 were built more durable than the MiG-25 so they will not be destroyed when the top speed of the Foxhound is achieved. And third, a second seat was added for a weapons system officer.
It is the heaviest interceptor in the world. It is even heavier than some commercial jet airliners.
The MiG-31 was first photographed by a Norwegian pilot over the Barents Sea in 1985.
It spread panic through the west after it started breaking many aviation records. It reached an absolute maximum altitude of 123,524 ft and set a time to height record of 4,000 m in 4 minutes, 11.78 seconds.
After the collapse of the Soviet Union, most of the MiG-31s were grounded. Once Russia got the money it needed, the Foxhound was back in active service.
The west believed the Foxhound to be a Super-Foxbat, but this turned out to be false, the Foxhound was in fact an entirely new model which only looked like the MiG-25.
The MiG-31 made no apperance in HAWX 1 before the "Russian Falcons" DLC pack was released even though the MiG-25 was modeled incorrectly as the Foxhound. It did make a full appearence in HAWX 2.