Certain commands designated by the Services as contracting activities. Also, the subordinate command in which the principal contracting office is located. It may include the Program Office (PO), related functional support offices, and contracting offices. The Defense Federal Acquisition Regulation Supplement (DFARS) lists the contracting activities. Examples are Naval Air Systems Command (NAVAIR) and Air Force Materiel Command (AFMC). Contracting activity is synonymous with Procuring Activity. The Head of Contracting Activity (HCA) has certain approval and authority responsibilities.