Conventional wellbore trajectory planning is commonly based on an Andersonian state of stress [SoS]. Based on various failure criteria the optimum well azimuth and inclination for a specific depth can be determined using stereographic projections of the safe mud weight window. For more complex geologic scenarios where the vertical and horizontal stresses are not principal stresses conventional wellbore trajectory planning has limitations. For an arbitrary non-Andersonian SoS safe trajectory orientations calculated for only a few locations along a well path will not be sufficient when determining an optimal trajectory for the entire well. In this paper a new methodology using the full stress tensor is developed to determine optimal well trajectories for complex in-situ stress scenarios. This study uses a 3D finite element analysis to simulate the SoS based on an integrated 3D MEM. The model yields the complete stress tensor at every location for a planned future well path. Using standard equations to determine the wellbore SoS for inclined wellbores the safe operational pressure window can be determined. This procedure is applied to multiple well trajectories of varying combinations of azimuth and inclination targeting a specific reservoir section.