A bypass turbojet engine for an aircraft, provided with a longitudinal axis (L-L) and comprising: - a nacelle delimiting, at the front, an air intake and axially containing a cold flow fan and a hot flow generator provided with a turbine enclosed in a casing ending, at the rear, in a bulbous boss connected to said turbine casing along a first connecting surface; - an engine cowl containing said hot flow generator and comprising:. an external wall delimiting with said nacelle a cold flow duct ending, at the rear, in a cold flow nozzle, and. an internal wall delimiting with said turbine casing a hot flow duct, - a hot flow nozzle extending said engine cowl rearward by being connected thereto along a second connecting surface and collaborating with said boss to delimit a nominal nozzle throat section and a nominal outlet section for said hot flow, and - at least one ventilation opening positioned between said external wall of said engine cowl and said hot flow nozzle, on the outside with respect to said cold flow nozzle, and intended to discharge to the outside a ventilation air flow bled from said cold flow and introduced into said engine cowl in order to regulate the temperature of said hot flow generator, characterized in that: - said hot flow nozzle consists of a single skin being at least approximately bulbous in shape, widening from said second connecting surface into the continuation of said external wall of said engine cowl; - said single skin collaborates with said boss to delimit said nominal nozzle throat section and said nominal outlet section for said hot flow; and - said ventilation opening is created in the vicinity of the largest-diameter part of said single skin. - a nacelle delimiting, at the front, an air intake and axially containing a cold flow fan and a hot flow generator provided with a turbine enclosed in a casing ending, at the rear, in a bulbous boss connected to said turbine casing along a first connecting surface; - an engine cowl containing said hot flow generator and comprising:. an external wall delimiting with said nacelle a cold flow duct ending, at the rear, in a cold flow nozzle, and. an internal wall delimiting with said turbine casing a hot flow duct,. an external wall delimiting with said nacelle a cold flow duct ending, at the rear, in a cold flow nozzle, and. an internal wall delimiting with said turbine casing a hot flow duct, - a hot flow nozzle extending said engine cowl rearward by being connected thereto along a second connecting surface and collaborating with said boss to delimit a nominal nozzle throat section and a nominal outlet section for said hot flow, and - at least one ventilation opening positioned between said external wall of said engine cowl and said hot flow nozzle, on the outside with respect to said cold flow nozzle, and intended to discharge to the outside a ventilation air flow bled from said cold flow and introduced into said engine cowl in order to regulate the temperature of said hot flow generator, - said hot flow nozzle consists of a single skin being at least approximately bulbous in shape, widening from said second connecting surface into the continuation of said external wall of said engine cowl; - said single skin collaborates with said boss to delimit said nominal nozzle throat section and said nominal outlet section for said hot flow; and - said ventilation opening is created in the vicinity of the largest-diameter part of said single skin.