620 ILCS 5/36
In exercising its powers and performing its functions under the laws of this State pertaining to aeronautics, and the rules, rulings, regulations, orders and decisions issued pursuant thereto, the Department, each officer thereof, and each employee designated by it, and such other departments, agencies, representatives, officers and employees of this State and of the municipalities and other political subdivisions thereof as may be designated by it, or who are charged with the enforcement of the laws of this State pertaining to aeronautics, whether or not designated by the Department to do so, shall have the right to enter upon the land within this State of any person, municipality or other political subdivision and enter the buildings and structures thereon for the purposes, when and to the extent that their duty so requires, of making surveys, ascertaining necessary facts, and making investigations relating to the State airport plan, a proposed or existing air navigation facility, any airport hazard, the obtaining of airport protection privileges, the establishment of zoning areas, the investigation of accidents concerning aircraft in this State, the condemning of property, the investigation of any violation of the laws of this State pertaining to aeronautics and the rules, rulings, regulations, orders and decisions issued pursuant thereto, and for any other purpose within the purview of the laws of this State pertaining to aeronautics and the rules, rulings, regulations, orders and decisions issued pursuant thereto; provided that such entry shall occur at reasonable times and with due regard for the safety of the owner, persons in possession or occupants thereof, and the protection of the buildings, structures, crops, or personal property located thereon; provided, further, that in the event any damage may be caused by virtue of any such entry, the Department may pay, as compensation, the amount of said damage as determined by it, in full satisfaction thereof, within the limits of available appropriations, or, if the Department does not pay the amount of any such damage, the person claiming compensation therefor may file his claim in connection therewith in the Court of Claims of this State.
620 ILCS 5/36