Abstract: A system, method and a computing architecture, for well path planning that can be used in directional drilling and provides for optimal path planning in directional drilling operations. One method includes receiving information about the planned drilling path, target-zone location and planned path changes, and real-time drill-bit location measurements. The method estimates the current state of the geometric location of the drill-bit in the earth during directional drilling operations, and the characteristics of the bottom-hole assembly before and after receiving drill bit location measurements. Such a method preferably determines a time optimal path, such as a Dubins path between the current state of the drill-bit location and the user-provided target-zone.