Propulsion assembly for an aircraft

A propulsion assembly for aircraft comprising a nacelle in which a turbojet engine is housed, the nacelle comprising:

• a downstream structure;
• and
• an upstream structure upstream of the downstream structure, said upstream structure comprising:
• an air inlet comprising an air inlet lip forming a leading edge of the nacelle, and
• a frame of the air inlet lip defining an annular partition separating the air inlet lip from a remainder of the air inlet of the nacelle and defining, with the air inlet lip, an air inlet box,
• the upstream structure being movable in translation along an axis substantially parallel to a longitudinal axis of the nacelle, alternately between a closed position according to which the upstream structure provides an aerodynamic continuity with the downstream structure of the nacelle, and an open position along which the upstream structure opens a passage in the nacelle so as to allow at least partial access to the turbojet engine,
• said propulsion assembly further comprising at least one locking/unlocking device adapted to alternately allow and prevent displacement of the upstream structure relative to the downstream structure, the locking/unlocking device being fastened on the frame of the air inlet lip and an upstream flange of the turbojet engine.