As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PHL - FLT 1040 - AIRCRAFT WOULD NOT PRESSURIZE AFTER TAKEOFF FROM PHL. FLIGHT RETURNED TO FIELD AND LANDED WITHOUT FURTHER INCIDENT. NO EMERGENCY WAS DECLARED. MAINTENANCE REMOVED AND REPLACED THE RIGHT PACK FLOW CONTROL VALVE. AIRCRAFT WAS PRESSURIZED TO 4 SPI. OPERATIONAL CHECK GOOD. (M)