For mission safety and efficiency, the airborne launch vehicle has to find an appropriate route to reach the mission goal satisfying some environment requirements and system constraints. A modified 3D waypoints generation path based on an improved version of the A* algorithm is proposed to find an optimal flight plan solution. This simple geometric path planning procedure can be implemented in real time in order to plan a new reference trajectory. In a presence of detected obstacles such as turbulence zones, no-fly zones, storms, etc., the information about the environment is regularly updated. This route reaches one or multiple goal points important for the mission success in order of their priority. The improved A* capabilities are tested via simulations in different scenario.