Flight safety and fuel consumption are major concerns of airline industry. En route civil aircraft may encounter hindrances such as bad weather patches, prohibited areas, and flight constraints. Robust path planning ensures maximum safety of the aircraft, crew members and passengers in unknown environment such as uncertain wind direction and drag from low pressure areas. This paper presents the robust path generation methodology near to the line of sight from starting aerodrome to the target aerodrome. This methodology confined the search space on the aerospace map to the nearby hindrance from the line of sight and then plan a robust path for the aircraft with the help of voronoi diagram. The voronoi diagram for the airspace map gives cells on the grid map, where each cell is equidistant from the hindrances. For these cells, the shortest robust path is evaluated using Dijkstra algorithm. The simulations for the shortest robust path on the airspace map were carried out for the proposed methodology and voronoi diagram for the full airspace map. The results obtained show that unnecessary clearances from the hindrances are avoided, and the computational time to evaluate the shortest robust path has been considerably reduced.