The department may by contract, lease, or other arrangement, upon a consideration fixed by it, grant to any qualified person for a term not to exceed twenty-five years the privilege of operating, as agent of the state or otherwise, any airport owned or controlled by the state: PROVIDED, That no such person shall be granted any authority to operate the airport other than as a public airport or to enter into any contracts, leases, or other arrangements in connection with the operation of the airport which the department might not have undertaken under RCW 47.68.130.