620 ILCS 50/9

"Airport Facilities" means any facility used in, available for use in, or designed for use in, air navigation, including airports and any structures, mechanisms, lights, beacons, marks, communicating systems, or other instrumentalities or devices used or useful as an aid constituting an advantage or convenience, to the safe taking-off, navigation, and landing of aircraft, or the safe, efficient and economical operation or maintenance of an airport, and any combination of any or all of such facilities.