The observed revenue service deterioration characteristics of the CF6-6D engine are analyzed to determine the detailed causes of the SFC and EGT increases. Cruise trend data from DC-10-10 revenue service operations and maintenance test cell results are utilized to define deterioration status. Effects of design changes and installation losses are included. Deterioration rates are seen to be reasonable compared to previous airline experience. Test results are presented for systematic performance field restoration of a deteriorated engine. Preliminary revenue service results are presented for the CF6-50 engine, the CF6 growth engine, which is installed on the DC-10-30, A300B and 747-200.