As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: FCU1 FAULT AT FL340. LOSS OF AUTOTHRUST. COULD NOT REENGAGE. DECESION MADE TO RETURN TO DFW NO EMERGENCY DECLARED AND LANDED OVERWEIGHT WITHOUT INCIDENT. MAINTENANCE REPLACED THE FLIGHT CONTROL UNIT PER AMM 22-81-12.