The unarmed 'B' version had greater impact than the interceptor when the USSR sent two MiG-25R and two MiG-25RB to Egypt in March 1971, which stayed until July 1972. They were operated by the Soviet 63rd Independent Air Detachment (Det 63), which was established for this mission. Det 63 flew over Israeli-held territory in Sinai on reconnaissance missions roughly 20 times. The flights were in pairs at maximum speed and high altitude, between 17,000 and 23,000 m (55,000 to 75,000 ft). On 6 November 1971, a Soviet MiG-25 operating out of Egypt flying at Mach 2.5 was met by Israeli F-4Es and fired upon unsuccessfully. A MiG-25 was tracked flying over Sinai at Mach 3.2 during this period. The MiG-25 engines went into overspeed, which led to them being scrapped. Det 63 was sent back home in 1972. Soviet-operated reconnaissance Foxbats returned to Egypt in 19–20 October 1973, during the Yom Kippur War. Det 154 remained in Egypt until late 1974.