Abstract: A propulsion air stream deflecting apparatus for an air cushion vehicle having a hull, an air duct mounted on the hull and a propeller fan, includes a plurality of rudders, each mounted on the hull adjacent to the rear open end of the duct for pivotal movement about a vertical axis. The rudders are adapted to close the rear open end of the air duct. A rudder control mechanism is operatively connected to the rudders for controlling the pivotal movement of the rudders to selectively provide a propulsion thrust and a steering thrust to the hull and to provide a closed position in which the rear open end of the air duct is closed by the rudders. A flap is pivotably mounted at the rear end thereof to the duct such that the flap closes an opening, formed at the rear end of the air duct, at a closed position thereof where the inner face of the flap is substantially flush with the inner surface of the air duct.