As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PHL-LGW - FLT 126 - CREW RECEIVED THE EICAS MESSAGE 'ATC FAULT' AND THE ASSOCIATED LIGHT. BOTH TRANSPONDERS WERE REPORTED TO BE INOPERATIVE. AFTER CONFERRING WITH MAINTENANCE, THE FLIGHT RETURNED TO PHL AND LANDED WITH NO FURTHER PROBLEMS. MAINTENANCE REPLACED THE ATC CONTROL PANEL. (M)