Whenever the Department of Aeronautics makes an order granting or denying a certificate of approval of an airport or a restricted landing area, or an original license to use or operate an airport, restricted landing area, or other air navigation facility, and the applicant or any interested municipality, within fifteen days after notice of such order has been sent the applicant by registered or certified mail, demands a public hearing, or whenever the department desires to hold a public hearing, before making an order, such a public hearing in relation thereto shall be held in the municipality applying for the certificate of approval or license or, in case the application was made by anyone other than a municipality, at the county seat of the county in which the proposed airport, restricted landing area or other air navigation facility is proposed to be situated, or the major portion thereof, if located in more than one county, at which hearing all parties in interest and other persons shall have an opportunity to be heard. Notice of the hearing shall be published by the department in a legal newspaper published in or of general circulation in the county in which the hearing is to be held, at least twice, the first publication to be at least fifteen days prior to the date of hearing. After a proper and timely demand has been made, the order shall be stayed until after the hearing, when the department may affirm, modify, or reverse it, or make a new order. If no hearing is demanded, as herein provided, the order shall become effective upon the expiration of the time permitted for making a demand. Where a certificate of approval of an airport or restricted landing area has been issued by the department, it may grant a license for its operation and use, and no hearing may be demanded thereon.