The close coupling of the ultra-high bypass ratio (UHBR) engine on a modern airliner poses a challenging task. The large engine nacelle diameter and a close coupling to the wing require slat cut-outs. In the attempt to remedy for the maximum lift loss, the Active Flow Control (AFC) is employed. The effect of steady suction and oscillatory blowing on local flow separation in the slat cut-out region downstream of a UHBR engine pylon is investigated by CFD URANS simulations. The simulation environment reflects the wind tunnel test conducted at the low speed wind tunnel at Tel-Aviv University. The validated CFD results are employed to assess the effects individual actuation mechanisms (steady suction, oscillatory blowing and a combination of both). Both investigated flow control mechanisms are effective in significant reduction of the flow separation. The AFC applied close to the leading edge in the slat cut-out region affects the flow field on large parts of the upper wing.