A bypass propulsion unit, comprising: - an engine, and - disposed around this engine, a nacelle defining a cold flow path, this nacelle including: - a nacelle cradle, intended to be linked to a suspension pylon of said propulsion unit, - a thrust reverser comprising cascades and at least one cowl, slidably mounted relative to the nacelle cradle, as well as thrust reverser flaps and connecting rods for actuating these flaps, - an inner structure wrapping said engine, and defining, with said movable cowl, a portion of said cold flow path, - a bifurcation for the passage of piping extending between said engine and the outside of said nacelle, diametrically opposite to said nacelle cradle, where - said thrust reverser comprises two structural half-shrouds (11a, 11b) disposed downstream of said cascades and secured thereto, - said inner structure comprises two upstream inner half-structures (32a, 32b), linked by their ends (35a, 35b, 37a, 37b) to said half-shrouds (11a, 11b) so as to form two half-sections of the cold flow path, these two half-sections being pivotally mounted on said nacelle cradle, this propulsion unit being characterized in that: - said thrust reverser flaps are hingedly mounted on said half-shrouds (11a, 11b), - said connecting rods are hingedly mounted on said thrust reverser flaps and on said upstream inner half-structures (32a, 32b), - said half-sections of the cold flow path are movable between a service position in which they bear on and on either side of said bifurcation, and a maintenance position, in which they are pivoted outwards of the nacelle, enabling access to the portion of the engine located below said upstream inner half-structures (32a, 32b). - an engine, and - disposed around this engine, a nacelle defining a cold flow path, this nacelle including: - a nacelle cradle, intended to be linked to a suspension pylon of said propulsion unit, - a thrust reverser comprising cascades and at least one cowl, slidably mounted relative to the nacelle cradle, as well as thrust reverser flaps and connecting rods for actuating these flaps, - a nacelle cradle, intended to be linked to a suspension pylon of said propulsion unit, - a thrust reverser comprising cascades and at least one cowl, slidably mounted relative to the nacelle cradle, as well as thrust reverser flaps and connecting rods for actuating these flaps, - an inner structure wrapping said engine, and defining, with said movable cowl, a portion of said cold flow path, - a bifurcation for the passage of piping extending between said engine and the outside of said nacelle, diametrically opposite to said nacelle cradle, - said thrust reverser comprises two structural half-shrouds (11a, 11b) disposed downstream of said cascades and secured thereto, - said inner structure comprises two upstream inner half-structures (32a, 32b), linked by their ends (35a, 35b, 37a, 37b) to said half-shrouds (11a, 11b) so as to form two half-sections of the cold flow path, these two half-sections being pivotally mounted on said nacelle cradle, - said thrust reverser flaps are hingedly mounted on said half-shrouds (11a, 11b), - said connecting rods are hingedly mounted on said thrust reverser flaps and on said upstream inner half-structures (32a, 32b), - said half-sections of the cold flow path are movable between a service position in which they bear on and on either side of said bifurcation, and a maintenance position, in which they are pivoted outwards of the nacelle, enabling access to the portion of the engine located below said upstream inner half-structures (32a, 32b).