The nacelle of the invention includes an air-inlet front section, a middle section for encasing the fan of the turbofan (7) and a rear section including means for connection to a pylon to be connected to the rigid structure or an airplane. The rear section includes a structural framework (18) having at least one aerodynamic smoothing and acoustic panel (21). The acoustic panel (21) is secured on the structural framework (18) by floating or elastic fixation means so that said acoustic panel (21) can be deformed in a direction (31) essentially centrifugal and radial relative to the turbofan (7) in the presence of overpressure air (3) in the engine compartment.