The aerodynamic character of station-keeping airships at high Reynolds numbers is examined. The boundary layer developing on the surface is sucked by an axial flow fan through a slot located at the rear part of the airship and the sucked gas is blown out as a jet. To know the effect of the cusp two models with and without a cusp attached to the inlet of the suction slot were used. The flow field near the inlet, in particular the pressure on the surface, was measured as the suction discharge was varied. We obtained the form drag by integrating the pressure distribution in a wide range of Reynolds number and of suction discharge. Taking into account the jet thrust and the calculated friction drag, we finally determined the total drag and evaluated the role of the cusp. It was found that the cusp plays an efficient role in reducing the drag.