A flow control system and method especially well adapted for use on a Coanda surface. In one embodiment a plurality of plasma actuators are disposed over a Coanda surface of a wing of an aircraft. The actuators are selectively energized to either delay the onset of boundary layer flow separation from the Coanda surface, or to promote flow separation. One embodiment discloses using dual mode plasma actuators on a Coanda surface. The system and method is applicable to a wide variety of aerodynamic surfaces where control over the separation of a boundary layer flow over a trailing edge surface is desired.