engines ended in the second half of 1939. Only two or four Pe-8s were equipped with them. Eighteen of the aircraft produced by the end of 1940 were fitted with AM-35A engines. In 1940, six aircraft without engines were fitted with Mikulin AM-35A engines, while VVS officials evaluated both the Charomskiy ACh-30 and Charomskiy M-40 aircraft Diesel engines. At least nine Pe-8s were fitted with diesel engines in 1941, but neither the ACh-30 nor the M-40 were entirely satisfactory, despite greatly increasing the range of the aircraft. All surviving Pe-8s were re-engined with AM-35As by the end of 1941. Production continued slowly at Factory No. 124; most of the factory's resources were devoted to the higher-priority Petlyakov Pe-2, a successful light bomber. At this time, most of these aircraft, re-designated as the Pe-8 after Petlyakov was killed in a Pe-2 crash on 12 January 1942, were built with out-of-production AM-35A engines. The 1,380-kW (1,850-hp) Shvetsov ASh-82 radial engine was proposed as a replacement to alleviate the shortage of engines and this modification went into production in late 1942. The exhaust arrangements of the ASh-82 were not compatible with the gun turrets in the rear of the engine nacelles and the guns were removed, reducing the aircraft's defensive capability. At the end of 1943, the nose turret was deleted in favor of a manually operated ShKAS machine gun in a more streamlined nose. This version of the aircraft proved to have much the same range as the diesel-engined versions, but reliability was greatly improved. Production of the Pe-8s totaled 93. The last Pe-8s were completed in 1944 as Pe-8ONs (Osobovo Naznacheniya—Special Mission) with Charomskiy ACh-30B engines and a fillet at the base of the vertical stabilizer. These were special VIP transports with a seating capacity of twelve and a cargo capacity of . Sources disagree if the armament was removed and, if it was, whether partly or entirely. Operational history Wartime use When Operation Barbarossa began on 22 June 1941, only the 2nd Squadron of the 14th Heavy Bomber Regiment (Tyazholy Bombardirovochnyy Avia Polk—TBAP), based at Boryspil was equipped with Pe-8s, but was not ready for combat. Two of its nine Pe-8s were destroyed by German air strikes shortly after the war began, before the Pe-8s were withdrawn out of reach of German bombers to Kazan. Stalin ordered that the squadron be reformed into a regiment, and that it strike targets