In 2012 and 2014 in collaboration with Siemens Industry Software, our team carried out a GVT of a F-16 in a Belgian airforce base. Preliminary linear analysis of the test results presents obvious symptoms of a nonlinear vibrating structure such as FRFs varying with forcing level and nonlinear distortion of the resonance peaks. This originate from stiffness and damping changes, and mode variability, typical of nonlinear structures. Nevertheless, linear tools can only hint at nonlinear behavior, they are ill-suited to properly study and characterize this dynamics, but also to properly confirm nonlinearity sources and location.