In the aerospace field, very strict regulations require equally rigorous design and testing of structures and systems to ensure they meet high safety and performance standards. Compliance with these standards necessitates advanced testing and monitoring techniques. Experimental or Operational modal analysis serves this purpose and allows for the identification of the dynamic properties of structures, but it can also be employed for the validation and refinement of finite element models or structural health monitoring. A Ground Vibration Test is a perfect example of the implementation of EMA for the dynamic characterization of aerospace structures. In these tests, hundreds of accelerometers are placed over the structure to measure its response to the controlled excitation provided by the shakers.