What was found
SHORTLY AFTER TAKEOFF, FLT ATTENDENT IN AFT CABIN REPORTED SMELL OF BURNING PLASTIC, ON DESCENT ODOR CHANGED TO OILY SMELL. SMELL ALSO NOTICED IN COCKPIT. CHECKED ALL C/B'S IN COCKPIT AND LOWER E/E. ALL OK, RAN PACKS AND RELATED EQUIPMENT FOR 4 HOURS. ALL OK. RAN BOTH ENGINES AT HIGH POWER, NO ODORS DETECTED. CHECKED APU INLET AND RAN APU, SYSTEM OK. A/C LATER DISPATCHED ON DOMESTIC FLIGHT, NO TROUBLES NOTED, NO ABNORMAL OIL USEAGE.