The UK is a world leader in the design, manufacture, and support of high-value aeronautic structures such as wings and jet engines. The UK's technology strategy is to reduce aeronautic structure weight by 35% by 2035 compared to 2019. Lighter structures are prone to complex nonlinear phenomena which cannot be identified and characterised using current ground vibration tests (GVTs). Building on recent advances in control-based continuation and nonlinear modal analysis, this project will develop a general and systematic GVT method that can overcome this issue. The method will be demonstrated on two academic benchmark structures before being tested on a full-scale aircraft structure thanks to an international collaboration with ONERA. The project will not only unlock the rigorous characterization of modal properties of nonlinear structures but will also bridge the gap currently preventing the development and validation of nonlinear models.