As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SEA - AIRCRAFT RETURNED TO FIELD WHEN HYDRAULIC PRESSURE INDICATED 0 AND QUANTITY INDICATED LOW. MAINTENANCE INSPECTED THE AIRCRAFT AND SERVICED THE NR 1 AND 2 HYDRAULIC SYSTEMS. OPERATIONAL CHECKS WERE PERFORMED AND THE AIRCRAFT WAS RETURNED TO SERVICE.