As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 6547 - IAD-ROA - DURING CRUISE, AIRCRAFT MADE AN UNSCHEDULED LANDING DUE TO NR 1 ALTITUDE INDICATOR FAILED. AIRCRAFT RETURNED TO GATE WITH NO FURTHER PROBLEMS. MAINTENANCE INSPECTED AND REMOVED AND REPLACED NR 1 ALTITUDE INDICATOR. OPS CHECK OK. AIRCRAFT WAS RELEASED AND APPROVED FOR RETURN TO SERVICE. (M)