This aircraft is reportedly the Ye-266M, which was a converted MiG-25RB modified with R15BF2-300 engines. On 31st August 1977, flown by MiG OKB Chief test pilot Alexander V.Fedotov, this aircraft set the absolute altitude record for a jet aircraft under it's own power, reaching 123,520ft. In fact, 'Ye-266M' was just a press name. The actual designation was E-155M. It is c/n N84019175.