A nacelle for an aircraft turbofan includes a rear section including a thrust reversal device having an upper door and a lower door, the upper and lower doors being mobile in rotation between a stowed position in which they are aerodynamically continuous with the rest of the nacelle and a deployed position in which the upper and lower doors are able to redirect forward the core and bypass flows produced by the jet engine, each door being moved from one position to the other by at least one dedicated actuator. The opening angle (X) of the upper door in the deployed position is smaller than the opening angle (Y) of the lower door.