Development of the R-40 started in the 1960s, to become the main weapon of the MiG-25 Foxbat Interceptor and was introduced under the designation R-40T (semi-active radar homing) and R-40R (infrared homing). The R-40 is the largest air-to-air missile currently in existence and it is currently used by the MiG-31 Foxhound.