The Polish government's Special Disaster Commission sent its findings on the cause of the accident to Moscow. In response, Russian engineers and scientists stated that the reasons given were implausible and that the turbine disintegrated "because of" engine failure, contrary to what was stated in the Polish report. (This could partially be attributed to a grudge Soviet engineers held against Poles, who purchased Ilyushin aircraft but replaced Ilyushin's own navigational systems with separately purchased, more modern American equipment.) Many years later it was revealed that after Flight 7's crash, all Il-62s used by Soviet officials and VIPs had their engines discreetly replaced with newer ones. At one occasion, a Polish governmental Il-62M had had specially installed newer engines for a joint Polish-Soviet governmental trip to Beijing; after that, the engines were taken back to the Soviet Union.