In any case where the Department refuses to issue a certificate of approval of or license or renewal of license for an airport, restricted landing area or other air navigation facility, or refuses to permit the registration of any license, certificate or permit, or refuses to grant a license to an air school or to an aeronautics instructor in ground subjects, or in any case where it issues any order requiring certain things to be done, or revoking any license or certificate, it shall set forth its reasons therefor and shall state the requirements to be met before such approval will be given, registration permitted, license granted or order modified or changed. Any order made by the Department under this chapter shall be served upon the interested persons by registered mail or in person. To carry out this chapter the Department, any member thereof, the Secretary of Transportation or officers or employees of the Department and any officers, state or municipal, charged with the duty of enforcing this chapter may inspect and examine at reasonable hours any premises, and the buildings and other structures thereon, where airports, restricted landing areas, air schools, flying clubs or other air navigation facilities or aeronautical activities are operated or carried on.