Fatigue test on a full scale panel with complex loading and geometry has been carried out using a tri-axial test machine specifically designed, built and located in the laboratory of the University of Naples. The aeronautical test panel was designed and manufactured by Alenia. The demonstrator is made up of two skins which are linked by a transversal butt-joint that is parallel to the stringer direction. A fatigue load was applied in the direction normal to the longitudinal joint, while a constant load was applied in the longitudinal joint direction. The demonstrator broke up after about 177000 cycles. Subsequently, a finite element analysis was carried out in order to correlate failure events; due to the biaxial nature of the fatigue loads, Sines criterion was used. The analysis was performed taking into account the different materials of which the panel is composed. The output shows good correlation between experimental data and numerical results, predicting the location on the panel exactly where the failure occurred.