620 ILCS 5/55
Proceedings may be initiated by applications, petitions, and complaints, including complaints made by the Department of its own motion. Any person, the Federal Government, or any agency, department or officer thereof, or any municipality or other political subdivision of this State or any other state, may make a complaint, which shall be in writing setting forth any act or things done or omitted to be done in violation or claimed to be in violation of the laws of this State pertaining to aeronautics, or of the rules, rulings, regulations, orders or decisions of the Department thereunder.
Upon the filing of a complaint, the Department shall cause a copy thereof to be served upon the person, municipality or political subdivision complained of, which shall be accompanied by notice requiring that the complaint be satisfied and answered within a reasonable time to be specified by the Department, or within the discretion of the Department, by a notice fixing a time when, and place where, a hearing will be had upon such complaint. If a hearing is prescribed by the Department, notice of the time and place thereof shall also be given to the complainant and to such other persons as the Department shall deem necessary. The Department shall have authority to hear and investigate any complaint notwithstanding the fact that the person, municipality or other political subdivision complained of may have satisfied the complaint.
The time fixed for such hearing upon a complaint shall not be less than ten days after the date of the service of such notice and complaint, unless the Department determines that an emergency exists, in which event it may prescribe a time for such hearing less than ten days after the date of such service.
The time fixed for any hearing, other than upon a complaint, under the laws of this State pertaining to aeronautics, or the rules, rulings, regulations, orders or decisions issued by the Department thereunder, shall not be less than ten days after the date of service of a notice in connection therewith upon the persons, municipalities or political subdivisions interested in the subject matter thereof, unless the Department determines that an emergency exists, in which event the Department may prescribe a time for such hearing less than ten days after the date of service of such notice. Such notice shall fix the time when and place where the particular hearing will be had, and shall give a general description of the subject matter.
Service in all investigations, inquiries and hearings before the Department may be made upon any person upon whom summons may be served in accordance with the provisions of the Civil Practice Law, as amended, and in accordance with all future amendments thereto and modifications thereof and the rules now or hereafter adopted pursuant to said Law, and may be made personally or by mailing same in the United States mails in a sealed envelope, registered, with postage prepaid. The provisions of this section as to notice shall apply to all hearings held by the Department or under its authority, under the laws of this State pertaining to aeronautics, and the rules, rulings, regulations, decisions and orders of the Department thereunder, except as otherwise specifically provided in any such law.
620 ILCS 5/55