50 ILCS 615/20

(a) With respect to any leased facility property used for airport purposes, at least 90% of the net proceeds of the lease shall be expended or obligated by the lessor municipality for: (i) the construction and maintenance of infrastructure within the municipality; (ii) contributions to pension funds created for municipal employees; or (iii) any combination of (i) or (ii). (b) The amount of net proceeds expended or obligated for item (ii) in subsection (a) may not exceed the amount of net proceeds expended or obligated for item (i) in subsection (a). As used in this Section, "net proceeds" means the gross proceeds less any debt service payments on, and payments to retire, debt that is specifically associated with the leased facility property or otherwise required to be paid out of lease proceeds.