In determining whether it shall issue a certificate of approval for any airport or restricted landing area, or any alteration or extension thereof, the Department shall take into consideration its proposed location, size and layout, the relationship of the proposed airport or restricted landing area to the then current national airport plan, the then current Federal airways system, the then current State airport plan, and the then current State airways system, whether there are safe areas available for expansion purposes, whether the adjoining area is free from obstructions based on a proper glide ratio, the nature of the terrain, the nature of the uses to which the proposed airport or restricted landing area will be put, the possibilities for future development, and such other factors as, under the circumstances, it regards as having an important bearing thereon.