620 ILCS 5/9

"Air navigation facility" means any facility other than one owned or controlled by the Federal Government, used in, available for use in, or designed for use in, aid of air navigation, including airports, restricted landing areas, and any structures, mechanisms, lights, beacons, marks, communicating systems, or other instrumentalities or devices used or useful as an aid, or constituting an advantage or convenience, to the safe taking-off, navigation, and landing of aircraft, or the safe and efficient operation or maintenance of an airport or restricted landing area, and any combination of any or all of such facilities.