A turbojet engine nacelle comprising: - a thrust reverser device and an actuating system of said thrust reverser device, said device comprising at least one movable cowl mounted in translation in a direction substantially parallel to a longitudinal axis of the nacelle between alternately a closing position in which it ensures the aerodynamic continuity of the nacelle and an opening position in which it opens a passage within the nacelle intended for a diverted flow directed towards the front of the nacelle in order to generate a thrust reversal; and - at least one section of gas ejection nozzle extending said movable cowl and including at least one nozzle flap movably mounted between a closed position in which the nozzle flap is folded back against the nozzle section in order to close a leakage passage towards the outside of the nozzle section and at least one open position in which said nozzle flap protrudes outwardly from the nozzle section and opens the leakage passage towards the outside of the nozzle; said nacelle being characterized in that said nozzle flap is pivotally mounted on the movable cowl and the actuating system comprises actuating means common to the movable cowl and to the nozzle flap, said actuating means being shaped to activate the displacement in translation of the movable cowl and the pivoting of the nozzle flap between the three following positions: - a first position called rest position in which the movable cowl is in its closing position and the nozzle flap is in its closed position; - a second position called opening position of the nozzle flap in which the movable cowl is in its closing position and the nozzle flap is in its open position; and - a third position called opening position of the movable cowl in which the movable cowl is in its opening position and the nozzle flap is in its closed position. - a thrust reverser device and an actuating system of said thrust reverser device, said device comprising at least one movable cowl mounted in translation in a direction substantially parallel to a longitudinal axis of the nacelle between alternately a closing position in which it ensures the aerodynamic continuity of the nacelle and an opening position in which it opens a passage within the nacelle intended for a diverted flow directed towards the front of the nacelle in order to generate a thrust reversal; and - at least one section of gas ejection nozzle extending said movable cowl and including at least one nozzle flap movably mounted between a closed position in which the nozzle flap is folded back against the nozzle section in order to close a leakage passage towards the outside of the nozzle section and at least one open position in which said nozzle flap protrudes outwardly from the nozzle section and opens the leakage passage towards the outside of the nozzle; - a first position called rest position in which the movable cowl is in its closing position and the nozzle flap is in its closed position; - a second position called opening position of the nozzle flap in which the movable cowl is in its closing position and the nozzle flap is in its open position; and - a third position called opening position of the movable cowl in which the movable cowl is in its opening position and the nozzle flap is in its closed position.