The office shall expend from funds for the purpose as appropriated by the general assembly and approved by the adjutant general sums needed to defray expenses incurred in rescue work, mercy missions, maintenance of an office, development of the aeronautical resources of the state, educational programs related to aviation, and air search and rescue, and for the upkeep of communications systems which have been, or are in the process of being, installed throughout the state. Only such sums shall be expended on communications systems as will be necessary for the procurement or replacement of equipment and not otherwise obtainable by grant or gift from any other source.