[3][4][5] The MiG-25 features a powerful radar and four air-to-air missiles, and it still has the world record for reached altitude of 38 km (125,000 ft).

The appearance of the MiG-25 sparked serious concern in the West and prompted dramatic increases in performance requirements for the American F-X fighter programme that lead to the McDonnell Douglas F-15 Eagle in the late 1960s.

The capabilities of the MiG-25 were better understood by the West in 1976 when Soviet pilot Viktor Belenko defected in a MiG-25 to the United States via Japan.

This meant not only dealing with accidental border violations but more importantly defending the vast airspace of the USSR against US reconnaissance aircraft and strategic bombers carrying free-fall nuclear bombs.

A major upgrade in the PVO defence system was required in order to meet the higher and faster American strategic bombers.

At the start of 1958, a requirement was issued for manned interceptors capable of reaching 3,000 km/h (1,600 kn) and heights of up to 27 km (89,000 ft).

Variable geometry would improve manoeuvrability at subsonic speed, but at the cost of decreased fuel tank capacity.

The perennial problem with engines dedicated to vertical lift is they become mere dead weight in horizontal flight and also occupy space in the airframe needed for fuel.

[19] Development of the MiG-25, which represented a major step forward in Soviet aerodynamics, engineering and metallurgy, took several more years to complete.

[21] The Mikoyan-Gurevich design bureau soon realized that the performance of the new aircraft gave it great potential to set new flight records.

Under Federation Aeronautique Internationale (FAI) classification, the Ye-155 type belonged to class C1 (III), which specifies jet-powered land planes with unlimited maximum take-off weight.

[13] Because of the thermal stresses incurred in flight above Mach 2, the Mikoyan-Gurevich OKB had difficulties choosing what materials to use for the aircraft.

The problem of cracks in welded titanium structures with thin walls could not be solved, so the heavier nickel steel was used instead.

[citation needed] Initially, the interceptor version was equipped with the TL-25 Smerch-A (also referred to as Product 720) radar, a development of the system carried by the earlier Tu-128.

By the time the MiG-25 entered service in 1969, this was a serious shortcoming, as strategic bombing doctrine was shifting towards low-level penetration of enemy territory.

After Belenko's defection to Japan exposed this flaw to the West, a government decree issued on 4 November 1976 called for urgent development of a more advanced radar.

The aircraft could carry unguided gravity bombs to fulfill a rudimentary strike role by using a delivery system developed for nuclear weapons.

The maximum speed of Mach 2.83 (3,000 km/h) is allowed to maintain no more than 5 minutes due to the danger of overheating of the airframe and fuel in the tanks.

Western intelligence first encountered the MiG-25 at the Moscow air show on 8 and 9 July 1967, where it was assessed as a fighter-bomber and all-weather interceptor capable of speeds in excess of Mach 2.5.

[30] NATO obtained a better understanding of the MiG-25's capabilities on 6 September 1976, when a Soviet Air Defence Forces pilot, Lt. Viktor Belenko, defected, landing his MiG-25P at Hakodate Airport in Japan.

The analysis, based on technical manuals and ground tests of its engines and avionics, revealed unusual technical information: As the result of Belenko's defection and the compromise of the MiG-25P's radar and missile systems, beginning in 1976, the Soviets developed an updated version with a new fire control system, the MiG-25PD ("Foxbat-E").

[40] Work was also carried out to improve the MiG-25's performance, with a revised version of the R15 engine, the R15BF2-300, designed with an extra compression stage and running at higher temperatures to give greater power and better fuel consumption.

According to research by journalist Tom Cooper, Iran claimed that ten MiG-25s (nine reconnaissance and one fighter) may have been shot down by Iranian F-14s (one kill was shared with an F-5[53]) during the Iran–Iraq war.

[N 1][71] In a different incident, two MiG-25s approached a pair of F-15s, fired missiles at long range which were evaded by the F-15s, and then outran the American fighters.

[62] After the war, on 27 December 1992, a U.S. F-16D downed an IQAF MiG-25 that violated the no-fly zone in southern Iraq with an AIM-120 AMRAAM missile.

[73] On 23 December 2002, an Iraqi MiG-25 shot down a U.S. Air Force unmanned MQ-1 Predator drone, which was performing armed reconnaissance over Iraq.

The Pakistani Government contended that the breaking of the sound barrier was a deliberate attempt to make the point that the Pakistan Air Force (PAF) had no aircraft in its inventory that could come close to the MiG-25's cruising altitude (up to 23,000 metres (74,000 ft)).

[79] India denied the incident but Pakistan's Foreign Minister, Gohar Ayub Khan, believed that the Foxbat photographed strategic installations near the capital, Islamabad.

[79][80] Lack of spare parts and India's acquisition of unmanned aerial vehicles and satellite imagery eventually led to its retirement in 2006.

Technicians started working on some of the airframes to press them back to service in the fight against the opposing internationally recognized Libyan government forces.