What was found
FLT JB919 JFK-ORD DECLARED AN EMERGENCY DUE TO HYDRAULIC SYSTEM 1 QUANTITY WAS LOW 0 PERCENT IN FLIGHT, NO LOW PRESSURE. A/C LANDED UNEVENTFULLY AND TAXIED TO THE GATE ON ITS OWN POWER. AT ORD MX SERVICED HYDRAULIC SYSTEM NR 1 IAW AMM 12-12-01 AND PERFORMED LEAK CHECK IAW AMM 29-00-01, NO LEAKS NOTED. AIRCRAFT RETURNED TO SERVICE. NEXT FLIGHT 900 ORD-JFK DURING FLIGHT AFTER 1 HOUR 45 MIN HYDRAULIC SYSTEM NR 1 LOST FLUID LANDED UNEVENTFULLY. JFK MX FOUND NR 1 ENGINE DRIVEN HYDRAULIC PUMP LEAKING, REMOVED AND REPLACED EDP NR 1 IAW AMM 29-11-01 SERVICED HYDRAULIC SYSTEM NR 1 IAW AMM 12-12-01, NO LEAKS NOTED. AIRCRAFT RETURNED TO SERVICE.