A 3-D A* mission planning/replanning algorithm satisfying both environmental constraints as static and mobile obstacles and kinematic and dynamic constraints coming from the aircraft limitations is proposed. This algorithm carries out the planning of the shortest path selected from the interconnections of several waypoints generated in the mission region. The shortest path is identified according to the presence of various obstacles during the path search, and its objective is to reach different goal points. Analysis of simulation results of this improved 3-D A *algorithm shows that it is adapted to different environments where more flight constraints can be considered, and it proposes an optimal solution to generate a free obstacle path. New trajectory plans can be generated from updated environmental data. In this specific launch mission for an autonomous airplane, the environmental uncertainties are important parameters.