In determining whether it shall issue a certificate of approval of a site or license for the use or operation of any proposed airport or restricted landing area, the Department shall take into consideration its proposed location, size and layout, the relationship of the proposed airport or restricted landing area to a comprehensive plan for statewide and nationwide development, 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, and the possibilities for future development.