Turbofan having a longitudinal axis and comprising a motor and a nacelle, surrounding the motor, which comprises a fan casing, in which a duct for a bypass flow is delimited between the nacelle and the motor and in which a flow of air flows in a flow direction, said nacelle comprising: - a fixed structure fixed to the fan casing, - a mobile assembly having a mobile cowl and a slider, the mobile cowl being fixed to the slider, the slider being mobile in translation on the fixed structure, in a direction of translation between an advanced position in which the slider is positioned such that the mobile cowl is moved close to the fan casing and a retracted position in which the slider is positioned such that the mobile cowl is moved away from the fan casing so as to define, between them, an open window between the duct and the exterior of the nacelle, and - a set of actuators causing the slider to move between the advanced position and the retracted position, and vice versa, the turbofan being characterized in that the nacelle comprises also: - a plurality of blades, each one comprising a first end mounted so as to be mobile in rotation on the slider about an axis of rotation, and where the blades are angularly offset from one to the next about the longitudinal axis, wherein each blade is mobile between a stowed position in which the blade is outside the duct and a deployed position in which the blade is across the duct, and - a manoeuvring system intended to move each blade from the stowed position to the deployed position and vice versa, where the manoeuvring system comprises: - for each blade, a shaft mounted so as to be mobile in rotation on the slider about an axis of rotation, and on which the blade is fixed, - for each shaft, an arm which has a first end fixed to the shaft and a second end, - an arc which is coaxial with the longitudinal axis and is mounted so as to be mobile in rotation, on the slider, about the longitudinal axis, - for each arm, a lever mounted in articulated fashion between the arc and the second end of the arm, and - an actuation system which rotates the arc in one direction and in the other. - a fixed structure fixed to the fan casing, - a mobile assembly having a mobile cowl and a slider, the mobile cowl being fixed to the slider, the slider being mobile in translation on the fixed structure, in a direction of translation between an advanced position in which the slider is positioned such that the mobile cowl is moved close to the fan casing and a retracted position in which the slider is positioned such that the mobile cowl is moved away from the fan casing so as to define, between them, an open window between the duct and the exterior of the nacelle, and - a set of actuators causing the slider to move between the advanced position and the retracted position, and vice versa, - a plurality of blades, each one comprising a first end mounted so as to be mobile in rotation on the slider about an axis of rotation, and where the blades are angularly offset from one to the next about the longitudinal axis, wherein each blade is mobile between a stowed position in which the blade is outside the duct and a deployed position in which the blade is across the duct, and - a manoeuvring system intended to move each blade from the stowed position to the deployed position and vice versa, where the manoeuvring system comprises: - for each blade, a shaft mounted so as to be mobile in rotation on the slider about an axis of rotation, and on which the blade is fixed, - for each shaft, an arm which has a first end fixed to the shaft and a second end, - an arc which is coaxial with the longitudinal axis and is mounted so as to be mobile in rotation, on the slider, about the longitudinal axis, - for each arm, a lever mounted in articulated fashion between the arc and the second end of the arm, and - an actuation system which rotates the arc in one direction and in the other.