Abstract: Modal tests and reduced order model have been used to investigate dynamic behaviour of a jointed structure made from thin metal sheets which has a large flat surface and has been assembled together by a number of scattered joints. An impact hammer and roving accelerometers were used in the modal tests to provide data to update the finite element model. NASTRAN Solution 103 was used to compute natural frequencies and modes of interest of the jointed structure. Meanwhile, NASTRAN Solution 200 coupled with the reduced order model was deployed to systematically improve the initial FE model of the jointed structure in the light of modal test results. The improvement of the initial FE Model was successfully and efficiently carried out via the reduced order model.