As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT NR 6418 - IAD-BOS - DURING CLIMB-OUT, RETURNED TO IAD DUE TO THE PRESSURIZATION BEING INOP IN BOTH AUTO AND MANUAL. AIRCRAFT LANDED AT IAD WITH NO FURTHER INCIDENTS. MAINTENANCE OPENED DMI NR 03558 IAW MEL 21-7-3. MAINTENANCE LATER CLEARED DMI NR 03558, BY REPLACING THE NEGATIVE PRESSURE AND REFERENCE PRESSURE FLEX HOSES TO PRESSURE CONTROLLER. AIRCRAFT WAS RELEASED AND APPROVED FOR RETURN TO SERVICE. (M)