What was found
OKC-ORD - FLT 1210 - DURING CRUISE, EXPERIENCED HYDRAULIC QUANTITY LOSS ON SYSTEM 1 AND HYDRAULIC QUANTITY LOW MESSAGE DISPLAYED ON MFDU. AC PROCEEDED TO ORD AND ACCOMPLISHED ALTERNATE LANDING GEAR AND FLAP EXTENSION, LANDING WITHOUT INCIDENT. REPLACED NR 1 HYDRAULIC SYSTEM ENGINE DRIVEN PUMP DUE TO LEAKING O-RING AT PRESSURE LINE. SERVICED HYDRAULIC SYSTEM AND ACCOMPLISHED LEAK AND GROUND CHECK WITH NO DEFECTS FOUND. SYSTEM GROUND CHECKED NORMAL OPERATION. (W)