In the last decade of the Cold War, the MiG-31, codenamed Foxhound by NATO, enjoyed a certain mystique in the West. The same grainy photos aerial photos of the high speed fighter would show up in aviation publications, along with ominous speculation over its capabilities. But unlike its peers—the MiG-29 and Su-27—the Foxhound never fully emerged from obscurity after the Cold War.
The reason is simple—the MiG-31 was built to be a home-defense interceptor, and was neither exported nor used in combat. But Moscow maintains hundreds of the fighters in its inventory as parts of its multi-layered air defense network, and will continue to do so for years to come.
The Foxhound emerged as an attempt to improve on a somewhat disappointing predecessor, the MiG-25 Foxbat. The twin-engine Foxbat remains the fastest flying operational fighter, able to attain speeds over Mach 3 and fly up to 70 thousand feet in order to counter the U.S. XB-70 Valkyrie supersonic bomber, which did not end up entering production. The Foxbat enjoyed an inflated reputation in Western aviation circles until Soviet defector Victor Belenko flew one over to Japan in 1976, allowing the Pentagon to discover what the Soviets had long been aware of—for all of its speed, the Foxbat was a bit of a dog when it came to maneuverability and could not maintain supersonic speeds at low altitude. Furthermore, it could attain Mach 3 speeds only by burning its engines out beyond their heat tolerance.
After the defection, the MiG-25 began to be sold for export, while the Soviet Union focused on building a better high-speed interceptor out of the Foxbat airframe. Moscow was no longer just concerned solely by high-altitude high-speed bombers, but also low-altitude cruise missiles zipping through gaps in its radar defenses. New design elements included a back seat Weapon Systems Officer to operate a powerful new radar, improved long range air-to-air missiles, and better engines.
This much evolved super Foxbat, designated the MiG-31, was distinguished by the addition of a backseat Weapon Systems Officer (WSO) to operate its large Zaslon S-800 Passive Electronically Scanned Array (PESA) radar. The heavy radar had a maximum range of 125 miles and featured “look down, shoot down” capability to detect and target low-flying aircraft, which was not widespread at the time. An infrared-red search and track system (IRST) further complimented it sensor suit.
The centerpiece of the Foxhound’s armament was its new R-33 long-range missiles, codenamed the AA-9 Amos by NATO. The R-33 are considered the Soviet equivalent to the AIM-54 Phoenix missiles used by U.S. Navy F-14s —the large radar-guided missiles were mounted under the MiG-31’s belly for engaging opposing bombers at long ranges of up to 75 miles. The Foxhound’s radar enabled it to launch at up to four aircraft simultaneously. Four to six additional medium- or short-range air-to-air missiles could be mounted under the wings. Unlike the Foxbat, the Foxhound was also armed with a 23-millimeter cannon.
The MiG-31 retains the Foxbat’s high-altitude performance, though it is a bit slower at Mach 2.83—still faster than any operation Western fighters today. More importantly, it can fly up to Mach 1.23 at low altitude—which the MiG-25 cannot. This makes it ideal for hunting ground-skimming cruise missiles and fighter bombers.
Nonetheless, the Foxhound is not highly maneuverable, and cannot safely pull more than 5Gs while flying supersonic. The MiG-31 would not fare well in air-to-air engagements against contemporary fighters such as the F-15—but that’s simply not what it was designed to do. The Foxhound is intended to close on intruders at high speeds, fire off its missiles and disengage.
Bane of the Blackbird
Production of the Foxhound began in 1979 and it entered service in 1981. Inspired by vague but glowing intelligence reports on its capabilities, the Foxhound acquired a sinister reputation in NATO intelligence reports. Reflecting this exaggerated reputation, the 1982 film Firefox, starring Clint Eastwood, imagined the MiG-31 as capable of flying at Mach 5, benefiting from stealth technology, and of being operated by thought alone!
In the real world, the MiG-31 does appear to have been used to chase after the SR-71 Blackbird spy plane , which could sustain speeds of Mach 3.3 or higher on its reconnaissance missions. The account  of one Soviet pilot suggests that a Foxhound was able to “lock on” to a Blackbird with its missiles. Another report claims that six MiG-31 were able to box-in a Blackbird in a separate incident. However, the Blackbird was never employed to actually overfly Soviet airspace, contrary to what some sources imply. The Blackbirds instead flew alongside it—which would explain why MiG-31 pilots never had reason to fire their R-33 missiles at the speedy spy planes.
Moscow refined its Foxhounds over time, starting with producing 101 of the air-refueling capable MiG-31DZ variant starting in 1989. Following the 1985 revelation that Soviet aeronautical designer Adolf Tolkachev had exposed the secrets of the Foxhound’s radar to the CIA , 69 MiG-31Bs and BSs were later developed with new radars and various hardware upgrades. Two MiG-31Ds were also developed to fire specialized anti-satellite missiles.
A MiG-31E export version was also conceived, but never saw foreign sales—the Foxhound was just too specialized and expensive to appeal to foreign buyers. The only Foxhounds serving outside of Russia are thirty to fifty inherited after the collapse of the Soviet Union by the Kazakh Air Force.
In 2015, there were rumors that Syria had purchased MiG-31s from Moscow. These did not prove to be true, probably to the good fortune of the Syrian government, which would have found little use for a high-performance air-to-air platform in its brutal civil war. Syria’s fleet of MiG-25 interceptors have already proven very poorly adapted to the conflict, reduced to firing air-to-air missiles at targets on the ground  with predictable results.
Foxhounds of the Future
According to one count, there are 252 MiG-31s in the inventory of the Russian Air Force. Moscow began modernizing its Foxhound fleet to the MiG-31BM and BSM variant starting in 2010, and plans to have 100 upgraded by 2020. The BM includes modernized cockpit displays, a hands-on-throttle-and-stick (HOTAS), and a new Zaslon-M radar with maximum detection range increased to 200 miles. It also is upgraded to employ the latest generation of long-range air-to-air missiles, including the R-33S, the R-77—the Russian equivalent to the U.S. AIM-120—and the super-long range R-37—intended to be a tanker- and AWACs-killer. The new Foxhounds are also capable of mounting up to 18 thousand pounds of air-to-ground smart bombs and anti-radar missiles in case Moscow needs some additional strike planes. Finally, the BMs have new data-links integrating the MiG-31’s sensors with ground-based radars and friendly fighter planes, allowing the Foxhound to coordinate the entire air defense system. A flight of four of the upgraded Foxhounds could patrol a swath of airspace over 400 miles across.
At 35 years old, the MiG-31 is expected to serve on until 2030. Moscow claims that another dedicated “Mach 4” interceptor, the MiG-41 or PAK-DP, will be developed to succeed the Foxhound in the air defense role. This is curious, as the Kremlin has only financed the production of 10 advanced PAK-FA stealth fighters  so far, giving reason to wonder if it can afford to deploy a far more specialized platform as well. Already, the project’s reported start date varies wildly in reports from 2013 to 2017 to 2019! Like other optimistic claims  made by the Russian defense sector, it would be wiser to take a wait-and-see approach rather than accept such claims at face value.
The MiG-31 is emblematic of an older design paradigm envisioning super-fast interceptors traversing vast distances to knock out encroaching bombers and missiles before they can do any damage. While the rest of the world has largely moved on to multi-role fighters that are equally capable of tangling with enemy fighters or launching air strikes against insurgents, the Russian military still sees a need for heavy, high-speed interceptors to guard its expansive borders.
Sébastien Roblin holds a Master’s Degree in Conflict Resolution from Georgetown University and served as a university instructor for the Peace Corps in China. He has also worked in education, editing, and refugee resettlement in France and the United States. He currently writes on security and military history for War Is Boring.