18.
In the initial period of fighting, the Ukrainian side tried using air forces. However, it soon appeared that separatists had well organised air defence systems at their disposal. The Ukrainian combat losses from April to the end of August 2014 amounted to 19 aircraft, 18 of which were lost during missions. Despite this, 17 helicopters were damaged and needed to land, 10 retreated after being damaged at airports. High losses and lack of effectiveness in operation eliminated Ukrainian air forces from the battlefield. M. Gawęda, Ukraińskie lotnictwo w wojnie o Donbas, Magnum-X, Lotnictwo 11/2014,
http://www.magnum-x.pl/ artykul/ukraiskie-lotnictwo-w-wojnie-o-donbas [accessed: 30.05.2015].