The subject of the invention is an aircraft nacelle in which an engine is placed, and which delimits a conduit (16) through which a flow capable of contributing to the thrust can pass, said nacelle comprising a device for reducing, canceling out or reversing the thrust comprising at least one flap (34) capable of occupying at least one so-called active position in which it diverts, in the direction of a radial opening, at least part of the flow capable of contributing to the thrust and another so-called rest position in which said flap (34) does not interfere with the flow capable of contributing to the thrust, the wall of the nacelle delimiting the conduit through which the flow to be diverted passes comprising at least one moving part capable of occupying two positions, a first positionin which it is interposed between the flow to be diverted and the flap (34); and another position in which it releases the flap (34) so as to allow said flap to change position and move from the restposition to the active position, characterized in that each flap (34) includes pivoting means (40) with a first pivot pin (42) placed at the level of a first so-called upper end of the flap (34) in the upper part of the nacelle and a second pivot pin (44) placed at the level of a second so-called lower end of the flap (34) in the lower part of the nacelle, said pivot pins (42, 44) being substantially parallel to the median vertical axis (26) of the nacelle.