In a bid find a suitable replacement for the venerable (though aging) MiG-31 "Foxhound" supersonic interceptor for the Soviet Air Force of the Cold War period, the Mikoyan concern drew up plans for a new high-speed interceptor under the "MDP" (translating to "Multirole, Long-range Interceptor") project designator. This later evolved to become the "MiG-701" (also the "Izdeliye7.01" or "Type 7.01"). Work began in or around 1980 while the company was still pushing ahead with the MFI 1.42 technology demonstrator (detailed elsewhere on this site), an aircraft intended to compete with the resulting design from the American Advanced Tactical Fighter (ATF) program which, eventually, produced the Lockheed Martin F-22 "Raptor" 5th Generation Fighter.
Mikoyan engineers drew up plans for a considerable larger aircraft than the in-service MiG-31. The MiG-701 was to have a twin, side-by-side engine arrangement involving air-breathing afterburning turbofans. These would be seated at the aft section of the dorsal spine, aspirating the pairing through rounded-rectangle intakes and exhausting through traditional exhaust ports at the rear. The plan form was of delta-wing with the mainplanes seated well aft of midships and canards would be installed closer to the cockpit for enhanced controlling. A tandem, twin-seat cockpit would be had aft of the radar-housing nosecone. A retractable tricycle arrangement was to provide the necessary gear for ground-running.
As drawn up, the aircraft was to feature an overall length of 30 meters with a wingspan of 19 meters. Maximum Take-Off Weight (MTOW) was rated at 65,000 kilograms. Performance estimates included a cruising speed of up to 1,553 miles-per-hour (2,500 kmh) with a range out to 6,835 miles (11,000 kilometers).
The rather optimistic project moved along rather slowly to the point that little tangible work had been completed by the time of the fall of the Soviet Union in 1989-1991. The MiG-701 program was cancelled in full in 1993 as Russian air industry restructured for challenging times ahead. Nothing more than drawings of the aircraft were completed before the end.
As a result, it was decided by the reborn Russian Air Force that the MiG-31 be modernized for an extended service life, one that would run into the mid-2020s and, perhaps, slightly beyond - by which point a worthy successor might be found. Other programs intended to replace the MiG-31 have included the MiG-301 and MiG-321, both originating in the 1990s.
To that point, the MiG-41 (PAK DP) is said to be currently (2020) under development with a first-flight planned for sometime in 2025. The design will feature 5th Generation qualities and incorporate stealth.