As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT NR 6424 - IAD-BUF - DURING CLIMB, AN UNSCHEDULED LANDING DUE TO RIGHT FLOW INOP. AIRCRAFT LANDED AT IAD AND RETURNED TO GATE NO FURTHER INCIDENTS. MAINTENANCE RESECURED LOOSE DUCT ON RIGHT ACM, PRESSURE AND OPS CHECK OK. AIRCRAFT WAS RELEASED AND APPROVED FOR RETURN TO SERVICE. (M)