A bypass propulsion unit, comprising: - an engine (M), 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 (M), and defining, with said movable cowl , a portion of said cold flow path , - a bifurcation for the passage of piping extending between said engine (M) and the outside of said nacelle, diametrically opposite to said nacelle cradle , where - said thrust reverser comprises two structural half-shrouds disposed downstream of said cascades and secured thereto, - said inner structure comprises two upstream inner half-structures , linked by their ends to said half-shrouds 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 , - said connecting rods are hingedly mounted on said thrust reverser flaps and on said upstream inner half-structures , - 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 (M) located below said upstream inner half-structures . - an engine (M), 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 (M), and defining, with said movable cowl , a portion of said cold flow path , - a bifurcation for the passage of piping extending between said engine (M) and the outside of said nacelle, diametrically opposite to said nacelle cradle , - said thrust reverser comprises two structural half-shrouds disposed downstream of said cascades and secured thereto, - said inner structure comprises two upstream inner half-structures , linked by their ends to said half-shrouds 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 , - said connecting rods are hingedly mounted on said thrust reverser flaps and on said upstream inner half-structures , - 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 (M) located below said upstream inner half-structures . <EOS>