A vertical tail unit for an aircraft, configured for flow control, comprising an outer skin in contact with an ambient air flow, wherein the outer skin extends between a leading edge and a trailing edge with two opposite lateral sides (27a, 27b), and surrounds an interior space, and wherein the outer skin comprises a porous section in the area of the leading edge, a pressure chamber arranged in the interior space, wherein the pressure chamber is fluidly connected to the porous section, an air inlet provided in the outer skin, wherein the air inlet is fluidly connected to the pressure chamber and configured to cause an overpressure in the pressure chamber such that air discharges through the porous section into the ambient air flow, and an air outlet provided in the outer skin, wherein the air outlet is fluidly connected to the pressure chamber and configured to cause an underpressure in the pressure chamber such that air of the ambient air flow is sucked in through the porous section, characterized in that the air inlet is formed as an opening that is arranged in one lateral side of the outer skin and that is flush with the outer skin, wherein the air inlet comprises an inward-pivoting door, wherein the door can be pivoted between a closed position where the ambient air flow is inhibited from passing through the outer skin and entering the vertical tail unit, and an opened position where the ambient air flow may pass through the outer skin into the vertical tail unit, and wherein in the closed position the door is flush with the outer skin, and in the opened position a channel is formed between the door and an edge of the opening for ambient air flow to pass through the outer skin into the vertical tail unit. an outer skin in contact with an ambient air flow, wherein the outer skin extends between a leading edge and a trailing edge with two opposite lateral sides (27a, 27b), and surrounds an interior space, and wherein the outer skin comprises a porous section in the area of the leading edge, a pressure chamber arranged in the interior space, wherein the pressure chamber is fluidly connected to the porous section, an air inlet provided in the outer skin, wherein the air inlet is fluidly connected to the pressure chamber and configured to cause an overpressure in the pressure chamber such that air discharges through the porous section into the ambient air flow, and an air outlet provided in the outer skin, wherein the air outlet is fluidly connected to the pressure chamber and configured to cause an underpressure in the pressure chamber such that air of the ambient air flow is sucked in through the porous section, characterized in that the air inlet is formed as an opening that is arranged in one lateral side of the outer skin and that is flush with the outer skin, wherein the air inlet comprises an inward-pivoting door, wherein the door can be pivoted between a closed position where the ambient air flow is inhibited from passing through the outer skin and entering the vertical tail unit, and an opened position where the ambient air flow may pass through the outer skin into the vertical tail unit, and wherein in the closed position the door is flush with the outer skin, and in the opened position a channel is formed between the door and an edge of the opening for ambient air flow to pass through the outer skin into the vertical tail unit.