When a user qualifies under the provisions of AFM 67-1, vol. 1, part three, chapter 1, Air Force Stock Fund and DPSC Assigned Item Procedures, 5 purchase of Air Force fuel and oil may be made on a cash or credit basis. An application for credit authority can be filed by submitting an Authorized Credit Letter to SA-ALC/SFRL, 1014 Andrews Road, Building 1621, Kelly AFB TX 78241-5603.