The Mig-31, manufactured by Russia's well known Mikoyan Gurevich company, is arguably the most advanced, if not the most maneuverable Russian fighter around. Nicknamed the "Foxhound," and derived from the infamous Mig-25 "Foxbat" the Mig-31 has the same top speed as its predecessor, as well as a second crew member to operate its massive radar.
The radar on the Foxhound is a "Zalson" phased array radar, and it is the most powerful radar ever fixed to any aircraft (although with a slightly longer range than the American F-14's radar, it cannot track an equal number of targets). In fact it is so powerful that the flight leader of a formation can act as a small AWACS (basically a giant plane with a giant radar) if linked to a ground radar and another air crew. It can also passively detect aircraft with a retractable infrared search-and-track sensor common to Russian aircraft, but rare on their western counterparts. The Mig-31 can even track and kill targets such as cruise missiles from ground level up to its maximum altitude.
Developed as an interceptor, the Foxhound has a greater range than its predeccesor, and can even fly over the entire North Pole. It also includes a tandem undercarriage for operating in the snowy Russian weather. Two hundred Mig-31's are in service today, but it is unlikely additional aircraft will be built due to defense cuts, and Russia's ailing economy.
A Mig-31 prototype, the Ye-155 broke the payload-to-height record in 1977, climbing to 121,622 feet with 4,400 pounds. A fully loaded Mig-31 weighs the same as four unloaded Mig-29's, and its cannon fires at a rate of 6,000 rounds per minute.
Type: Two engine high-performance interceptor
Powerplant: Two PNPP(Solvoviev) D-30F6 turbofan engines each rate at 20,940 lbs of thrust, or 34,111 lbs with afterburner.
Max Speed: 1,850 mph at 57,400 ft.
Ceiling (Maximum Altitude): 67,568 ft.
Ferry Range: 2,046 miles
Weights: Normal takeoff 90,200 lb.; maximum takeoff 101,640lb.
Weapons: One Gsh-6-23 six barrel 23-mm Gattling cannon with 250 rounds; various air-to-air missiles including R-40 "Acrid", R-60 "Aphid" and R-33 "Amos" missiles.
Span: 44 ft.
Length: 74 ft.
Height: 20 ft.
Wing area: 663 sq. ft.
*-Some of this information was obtained from "Aircraft of the World: A Complete Guide"