Mont. Code Ann. § 67-11-222

The department may control the operation of airports constructed under the provisions of 67-11-221 and may provide for the imposition of landing fees, granting of fuel and service concessions, or the lease of portions of the premises for other related airport services or for purposes not inconsistent with the use of the premises for airport purposes. All income from the operation of such airports shall be deposited in the state treasury in the airport operating account within the enterprise fund. All expenditures from the account shall be within the limits of legislative appropriations and shall be made upon vouchers signed and approved by the director of the department.