A hybrid mesh generation method is presented to discretize the computational domain around complex aerodynamic geometries. The idea behind this hybrid method is to combine the orthogonality and regularity of structured grids inside the boundary layer, the efficiency and simplicity of Cartesian grids and the flexibility of unstructured grids for development of an automatic, robust and fast mesh generation method. A series of structured layers is firstly generated around wetted surfaces. Cartesian grids are then constructed using a binary tree data structure covering the rest of the domain. Those Cartesian cells overlapping with the structured grids are then removed. Finally, unstructured triangular cells are generated to fill all empty regions in the domain as a result of the trimming method process. The developed method is used for calculation of a number of laminar and turbulent flow test cases. Results show that the presented grid generation method can compute viscous flows with good accuracy and less computational time.