423 by bombers. During this short war 135 flight crew members and 576 ground personnel lost their lives. About 300 Royal Yugoslav Air Force personnel evacuated, first to Greece then to Crete. After the Battle of Crete they went on to the deserts of the Near and Middle East, where for a short time they found a safe place. In June 1941 the 20th Hydroaviation Squadron under command of Lieutenant Vladeta Petrović with their no surrender war flag was renamed in the 2nd Yugoslav Squadron, attached to No. 230 Squadron RAF. Up until 23 April 1942 the squadron flew 912 combat mission (1,760 flying hours) and lost four aircraft. The main mission of the squadron was anti-submarine patrol and protected allied shipping. Socialist Yugoslavia After World War II the Air Force underwent several developmental stages, the first major air force modernization being performed from 1953 to 1959. Aircraft made in the West (such as German Dornier Do 28) were introduced thus broaching the era of jet aviation. With the forming of first helicopter squadron in 1954 the chopper units were also incorporated within the reorganised Air Forces branch, renamed to Yugoslav Air Force (Jugoslovensko ratno vazduhoplovstvo). At the beginning of 1960s Soviet supersonic fighter MiG-21 was introduced, followed by intensive growth of Yugoslav aviation industry in that period. A number of jet planes prototypes were constructed, which served as basis for the development of training fighters and fighter aircraft, such as Soko G-2 Galeb and J-21 Jastreb, G-4 Super Galeb and Soko J-22 Orao and the most advanced Soviet fighter aircraft MiG-29 was introduced in the late 1980s. Yugoslav Wars In June 1991 the Slovenes resistance to re-imposition of federal control over Slovenia rapidly escalated into an armed conflict with Yugoslav People's Army. During the Ten-Day War in Slovenia two Yugoslav Air Force helicopters were shot down, while it launched air strikes on TV transmitters and Slovenian territorial defence positions. During the War in Croatia, the Yugoslav Air Force was active providing transport and close air support missions to Yugoslav Ground Forces, but was gradually forced to abandon air bases outside of ethnic Serbian held areas. The Yugoslav Air Force equipment in Bosnia and Herzegovina was given to the new Republika Srpska Air Force and used during the War in Bosnia. In 1991 and 1992, the Yugoslav Air Force lost a total of 46 airplanes and helicopters in Slovenia, Croatia