As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BOS/JFK - FLT 6439 - DURING CRUISE AT 1800 HRS ON 4-13-98, AIRCRAFT MADE AN UNSCHEDULED LANDING AT BOS DUE TO NR 2 AHRU FAILED. AIRCRAFT RETURNED TO GATE WITH NO FURTHER PROBLEMS. AIRCRAFT FERRIED TO IAD WHERE MAINTENANCE INSPECTED AND REMOVED AND REPLACED AHRS. OPS CHECK OK. AIRCRAFT WAS RELEASED AND APPROVED FOR RETURN TO SERVICE. (X)