A turbomachine for an aircraft including at least one turbine driving rotation of a fan, and a jet nozzle coaxially extending a turbine and creating, with an outlet cone that terminates the turbine, a passage of annular cross section for combustion gases that pass through the turbine. The jet nozzle can be mounted so that it can move between two extreme positions for which under action of a controller, an annular cross section of the passage for the gases is respectively at its minimum or maximum, making it possible to vary the cross section according to phases of operation of the aircraft and distribute thrust between the fan and the jet nozzle.