superior performance and an increased maximum payload of 14.5 Tonnes (31,970 lb). The auxiliary endplate fins eventually gave way to improved splayed ventral fins under the rear fuselage. The directional stability was now acceptable and the new ventral fins also improved longitudinal stability at high g and on landing approach, as well as delaying the onset of Mach buffet to M0.702. Due to being sited in an area of flow separation, the new ventral fins also caused unpleasant vibrations. Following results of flight tests and at least two fatal crashes, an effective tailplane deicing system was retrofitted to all remaining aircraft. Operational history A total of 104 aircraft were built, including the prototype and static test airframes, entering service with the Ukrainian Civil Aviation Directorate of Aeroflot from 27 April 1959, proving popular due to large cargo volume (when fitted with reduced seating) and excellent field performance, making the aircraft suitable for use on small undeveloped airfields. The Antonov Bureau simultaneously developed and produced the Antonov An-8 medium military transport, the An-10 civil airliner and military paratroop transport, as well as the Antonov An-12 military cargo transport. On 16 November 1959 CCCP-11167 crashed on final approach near Lviv due to icing. On 22 April 1962 an An-10A piloted by A. Mitronin achieved a world record 500 km closed loop speed record averaging . On 26 February 1960, at Lviv Danylo Halytskyi International Airport, CCCP-11180 crashed due to reduced longitudinal stability and control authority caused by icing of the tailplane. Military use of the An-10 was fairly extensive with 45 An-10TS built for the VTA, 16 flown exclusively by military units and the remaining 38 loaned to the Ministry of Civil Aviation, as well as the flyable aircraft remaining after withdrawal from Aeroflot service. On 18 May 1972, while descending to Kharkiv International Airport an An-10 crashed, killing eight crew and 113 passengers. An investigation revealed fatigue cracking of the wing centre section stringers on many of the remaining aircraft. Following this accident, Aeroflot ceased operating the An-10. After withdrawal from Aeroflot service on 27 August 1972, 25 An-10A aircraft which were in good condition were transferred to the VVS (Soviet Air Force) and other MAP (Ministry of Aircraft Production) units, until retired by 1974. A few examples have been preserved as exhibits in museums, and several have been converted into children's theatres (at Kyiv, Samara and Novocherkassk). Operators Aeroflot Soviet