S.D. Codified Laws § 50-7-5
Any power granted by this chapter to counties and municipalities may be exercised jointly by the county and municipalities located in the county or abutting county. In the case of any existing airport owned by a municipality, the county in which the municipality is located, or an abutting county, may purchase from the municipality an interest in the airport. In the case of any airport operated by a county, a municipality in the county or abutting county may purchase from the county an interest in the airport and may appropriate money and do all other things necessary to share in the operation expense as if the airport was owned and operated solely by the county or municipality. In case of a jointly owned and operated airport the management of the airport shall be in accordance with regulations adopted by the governing boards of the county and municipality not inconsistent with other provisions of this chapter, and the governing boards of the county and municipality may by resolutions of their respective governing bodies create an airport board.
SDCL 50-7-5