1. A computer-aided method suitable for assisting in the design of an aircraft by providing dimensioning aerodynamic forces, skin values or values distributions around an airfoil corresponding to an aircraft component in transonic conditions inside a predefined parameter space by means of a reconstruction of previously performed CFD computations for an initial group of points in the parameter space using a reduced-order model, generated by computing Proper Orthogonal Decomposition (POD) modes of flow variables and obtaining POD coefficients using a genetic algorithm (GA) that minimizes error associated to the reduced-order model, wherein said method comprises the following steps: a) Decomposing for each flow variable the complete flow field (CFF) into a smooth field (SF) and a shock wave field (SWF) in each of said computations for an initial group of points obtained by said previously performed CFD computations; b) Obtaining the POD modes associated with the smooth field (SF) and the shock wave field (SWF) for all said computations by the following sub-steps: b1) Obtaining the internal shape of the shock wave by POD methodology; b2) Dividing the smooth field (SF) into two regions, pressure region and a suction region; b3) Selecting a set of computations to calculate POD modes of the smooth field (SF); b4) Obtaining the smooth field (SF) and the complete flow field (CFF) by POD methodology; b5) Obtaining an initial guess of POD mode amplitudes; c) Obtaining the POD coefficients using a genetic algorithm (GA) that minimizes a fitness function defined using a residual calculated from Euler equations and boundary conditions of the previously performed CFD calculations; d) Calculating said aerodynamic forces, skin values or values distribution for a combination of values of said parameters using the previous steps.