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.