 "Gruppe" flew combat air patrols in the area of Venlo–Tirlemont–Liège and later that day to Maastricht.The following day, Balthasar claimed three Belgian Air Force Gloster Gladiator fighters and a French Air Force Morane-Saulnier M.S.406 fighter in the combat area of Maastricht.Four Belgian Air Force Gladiators from 1/I/2 (1st Squadron, 1st Group, 2nd Wing) were shot down by 1./JG 1 on 13 May while flying a fighter escort mission for Belgian bombers, although the Germans claimed seven, only six were sent on the mission.