The automatic motion or trajectory planning is essential for several tasks that lead to the autonomy increase of Unmanned Aerial Vehicles (UAVs). This work proposes a Dijkstra algorithm for fixed-wing UAVs trajectory planning. The navigation environments are represented by sets of visibility graphs constructed through the terrain elevations of these environments. Digital elevation models are used to represent the terrain elevations. A heuristics to verify if a trajectory is collision-free is also proposed in this work. This heuristics is a method of grid-based local search which presents linear computational time
is the number of verification steps. This heuristics is compared with another method for collision verification. Results are presented in this work.