35 ILCS 200/10-95
The person liable for taxes on land used for airport purposes must file a verified application requesting the additional valuation provided for in Section 10-90, with the chief county assessment officer of the county where the land is located, by January 1 of each year for which that valuation is desired. The application shall be in the form prescribed by the Department and contain such information as may reasonably be required to determine whether the applicant meets the requirements of Section 10-90. If the application shows the applicant is entitled to the valuation, the chief county assessment officer shall approve it; otherwise, he or she shall reject the application.
When an application has been filed with and approved by the chief county assessment officer, he or she shall determine the valuation of the land in two ways as otherwise permitted by law, and as described in Section 10-90, and shall list those valuations separately. The county clerk, in preparing assessment books, lists and blanks under Section 9-100, shall include columns for indicating the approval of an application filed under this Section and for setting out the valuations made as otherwise permitted by law, and under Section 10-90.
35 ILCS 200/10-95