As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS DECLARED AND THE AIRCRAFT RETURNED TO LAS DUE TO A YELLOW HYDRAULIC SYSTEM RESERVOIR LOW PRESSURE MESSAGE ON DEPARTURE SHORTLY AFTER FLAP RETRACTION. THE AIRCRAFT LANDED SAFELY AT LAS WHERE IT WAS TOWED TO THE GATE. **SUPPLEMENTAL REPORT WILL BE SUBMITTED** (OPEN)