(1) If an authority should realize a surplus, whether from operating the airport or leasing it for operation, over and above the amount required for the maintenance, improvement, and operation of the airport and for meeting all required payments on its obligations, it shall set aside the reserve for future operations, improvements, and contingencies as it shall deem proper and shall then apply the residue of the surplus, if any, to the payment of any recognized and established obligations not then due.
(2) After all the recognized and established obligations have been paid and discharged in full, at the end of each fiscal year the authority shall set aside the reserve for future operations, improvements, and contingencies as prescribed in subsection (a) of this section and then pay the residue of the surplus, if any, to the counties, municipalities, and the state in direct proportion to their financial contribution.
(3) No such distribution of the residue of the surplus shall violate United States law or the terms of any deed, grant agreement, or other agreement with the United States.