Key point: The MiG-31 was great for patrolling Russia’s vast airspace.
During the Cold War, the Soviet Union’ s Air Defense Forces (VPVO) needed a series of heavy interceptors to patrol its massive borders. Most regular “light” fighters like the early MiGs were not up to the task, as they lacked the range and speed to intercept to rapidly climb and intercept supersonic American bombers, who were expected to zoom over the Arctic to drop bombs on the Soviet Union.