70 ILCS 5/13.3
An airport authority that has prepared a capital improvement program under Section 13.2 may, in its annual appropriation ordinance, appropriate an amount not to exceed 3% of the equalized assessed value of property subject to taxation by the airport authority for the purpose of making specified capital improvements, acquisitions, repairs, or replacements of the airport authority's real property or equipment or tangible personal property. The amount appropriated for that purpose shall be deposited into a special fund known as the Capital Program Fund. Expenditures from the Capital Program Fund must be budgeted in the fiscal year in which the capital improvement, acquisition, repair, or replacement will occur. If any surplus moneys remain after the completion or abandonment of any object for which the Capital Program Fund was established, the moneys no longer necessary for capital improvement, acquisition, repair, or replacement shall be transferred into the airport authority's general corporate funds on the first day of the fiscal year following the abandonment or completion of the project or the discovery of the surplus moneys.
70 ILCS 5/13.3