620 ILCS 5/64
Anything in the laws of this State pertaining to aeronautics to the contrary notwithstanding, the Department may at any time amend, change, abrogate or rescind any rule, ruling, regulation, decision or order made by it: provided, that when such rule, ruling, regulation, order or decision, sought to be so amended, changed, abrogated or rescinded, was prescribed or issued by requirement of law, after notice and an opportunity to be heard, the Department shall give notice and an opportunity to be heard to the persons, municipalities, or other political subdivisions to be affected thereby, before making such amendment, change, abrogation or rescission thereof. Any order amending, changing, abrogating or rescinding a prior rule, ruling, regulation, order, or decision shall, when served upon the persons, municipalities, and other political subdivisions affected, have the same effect as is herein provided for original rules, rulings, regulations, orders and decisions. Within thirty days after the service of any rule, ruling, regulation, order or decision of the Department, any party to the action or proceeding, or other persons, municipalities or political subdivisions affected, may apply for a rehearing of said rule, ruling, regulation, order or decision in respect to any matter connected therewith, specified in the application for rehearing. The Department shall receive and consider such application and shall grant or deny the same within twenty days from the date of the receipt thereof by the Department. In case the application for rehearing is granted, the Department shall proceed as promptly as possible to consider the matters presented by such application. No appeal shall be allowed from any rule, ruling, regulation, order or decision of the Department unless and until an application for a rehearing thereof shall first have been filed with and acted upon by the Department.
No person, municipality or other political subdivision in any appeal shall urge or rely upon any grounds not set forth in such application for rehearing before the Department. An application for rehearing shall not excuse any person, municipality or other political subdivision from complying with and obeying any rule, ruling, regulation, order or decision of the Department, or any requirement contained therein, theretofore made, or operate in any manner to stay or postpone the enforcement thereof, except in such cases and upon such terms as the Department may by order direct. If, after such rehearing and consideration of all the facts, including those arising since the making of the rule, ruling, regulation, order or decision, the Department shall be of the opinion that the original rule, ruling, regulation, order or decision, or any part thereof, is in any respect unjust or unwarranted or should be changed, the Department may amend, change, abrogate or rescind the same. A rule, ruling, regulation, order or decision made after such rehearing, amending, changing, abrogating, or rescinding the original rule, ruling, regulation, order or decision, shall have the same force and effect as the original rule, ruling, regulation, order or decision, but shall not affect any right or the enforcement of any right arising from or by virtue of the original rule, ruling, regulation, order or decision unless so ordered by the Department.
Only one rehearing shall be granted by the Department, but this shall not be construed to prevent any person, municipality or other political subdivision from filing a petition setting up a new and different state of facts after two years, and invoking the action of the Department thereon.
620 ILCS 5/64