Finally, in 1944, he found an aircraft that he deemed a worthy heir: the Lavochkin La-7. However, one of his close friends, Soviet ace Alexander Klubov, was killed in a landing mishap while converting to the La-7. The crash was blamed on the malfunction of the plane's hydraulic system. Pokryshkin subsequently cancelled his regiment's conversion, and there are multiple reports that they instead began flying the Bell P-63 Kingcobra. Through the Lend-Lease agreement with United States, the Soviet Union was not allowed to use P-63s against Germany; they were given only to be used in the eventual battle with Japan. Thus it is quite understandable that no mention of this appears in any official records. However, personal accounts of German pilots and flak crewmen who encountered P-63s in the skies of Eastern Prussia as well as in the memoirs of one of the pilots in Pokryshkin's squadron. It is reported that 9th Fighter Aviation Division was given approximately 36 P-63s but these were not used while the fighting was still in progress.