B787-900
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 137.25; Flight Crew Total 11289.93; Flight Crew Type 2095.00
Aircraft Equipment Problem Less Severe
Air Traffic Control Provided Assistance; Flight Crew Overcame Equipment Problem; Flight Crew Returned To Clearance
Aircraft
Our left pack was deferred and MELed for several days before flight. The Captain accepted the aircraft with the deferral. Approximately 5 hours into the flight; we climbed to FL370. Shortly after reaching FL370; we heard several surging sounds from the pressurization system and we felt a shutter once in the airframe. We called Maintenance and decided with their explanation of the deferral; we would try FL360. While at FL360 we felt no more shutters in airframe and heard no more surges in pressure. The captain thought it was prudent; and the safest course of action; to limit our altitude to FL360 or lower; for the rest of the flight. We continued the flight with no further issues and we wrote it up in log book.
B787 First Officer reported resolving pressurization system malfunction during cruise.