For the purpose of equipping, improving, operating, maintaining and regulating public airports, and all things incidental thereto, and to pay a portion of the principal and interest on bonds issued under the authority of K.S.A. 12-1774, and amendments thereto, by cities located in the county, said board of county commissioners hereby is authorized to levy an annual tax in an amount necessary to pay the cost thereof.
K.S.A. 3-307