70 ILCS 5/9.3

Whenever any incorporated territory, containing 60 acres or less, is wholly bounded by any airport authority organized under this Act, that territory may be annexed by that airport authority by the passage of an ordinance to that effect by the Board of Commissioners of the airport authority, describing the territory to be annexed. After the passage of such ordinance of annexation, a copy of such ordinance, with an accurate map of the territory annexed, certified as correct by the Secretary of the Board of Commissioners, shall be filed with the Recorder of the County in which the annexed territory is situated.