Isthmus of Perekop
By the end of year his score was 27. Hackl became an "ace-in-a-day" for the first time on 19 April 1942, claiming two Mikoyan-Gurevich MiG-3, two Polikarpov R-Z and one I-18 shot down over the Isthmus of Perekop. His score increased further, and by May 1942, after 51 victories he received the Knight's Cross of the Iron Cross (). During the month of July 1942, Hackl claimed 37 enemy aircraft shot down in the aerial battles around Voronezh, including 6 victories in a day on both 21 and 23 July. In August 1942, he claimed 14 further victories which included his 100th claim on 3 August. He was the 16th "Luftwaffe" pilot to achieve the century mark.