Most numbered type of bomber in the Yugoslav Kingdom was Dornier Do17K and units operated German and Yugoslav built machines. They were stationed in the South Serbia and planed to take aggressor action against possible invader in this area. It is true that most successful action was taken by this unit and by this type of airplane but this could be even more effective if they could manage to safe bulk of their airplanes lost in the first day of hostilities.
I have chance to talk with veterans and read memories about this first day disaster over the unit stationed at Skoplje airfield. Whole group disappeared in the surprising German low level attack and just few airplanes survived and continued combat.