Date: 202111
Local time of day: 1801-2400
Location: ZZZZ.ARTCC, FO
Flight conditions: VMC
Aircraft: B787 Dreamliner Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
ATC / advisory: Center ZZZZ
Aircraft component: Air Conditioning and Pressurization Pack
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; First Officer
Reporter qualification: Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Human factors: Workload; Troubleshooting; Time Pressure
Second reporter function: Relief Pilot; First Officer
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Automation Aircraft Other Automation; Person Flight Attendant; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Landed in Emergency Condition; Flight Crew Overcame Equipment Problem; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Returned To Departure Airport; General Flight Cancelled / Delayed
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: Departed ZZZZ enroute to ZZZ1. As climbing through FL370; my ears were hurting. At that moment; we had an EICAS message that said Left Pack Inop". We started the checklist; which instructed us to descend below FL350. ATC gave us FL300. As we started to descend; the cabin altitude status page appeared on the EICAS. The cabin altitude was rising above 9;500 at a good rate. We reset the left pack as the checklist instructed. It reset; but the cabin altitude was still climbing through 10;000 feet. We coordinated with ATC; donned oxygen masks; and started an expedited descent to 15;000; as we had terrain considerations. We finally started to gain control of the cabin altitude. It had peaked at 11;600 feet MSL. As the Relief Officer had vacated the crew rest and was now back in the flight deck; and we were removing our masks; there was a strong burning odor. The flight attendants were calling and reporting the strong odor as well; while the FA in the back said they had smoke. At this time the flight deck was very warm; the Relief Officer said the crew rest was very warm; and there was hot air coming out of the air vents in the flight deck. At this point we thought we had a fire; we requested special handling; and used [Captain's] authority to fly back as fast as possible to ZZZZ. We flew an ILS approach to Runway XX and did an autoland to help with workload. Lack of fire indications; and confirmation from [support] vehicles helped with the decision to taxi back to terminal. It took 2.5 hours to deplane everyone from the hardstand; as customs and airport staff go home after [the last flight departs]."


Second narrative: In the bunk starting my rest break.  Noticed it was very stuffy and no air from vent.  Felt airplane start a descent and heard speed brakes deployed.  Got dressed; exited the bunk and went to the cockpit.  Odor of smoke was present in galley and I could hear the pilots and knew they had oxygen masks on.  Got onto flight deck; donned my oxygen mask; and began to assess and help the crew with checklists and navigation. Cabin pressure was regained at approximately FL150.  Checklists completed.  Odor of smoke was becoming noticeable.  I spoke with F/A's (Flight Attendants) and had them walk the cabin.  They reported strong odors but no visual of smoke.  Decision was made to turn around and head to ZZZZ primarily due to the odor and the [mountainous terrain] on our nose.  Masks were never deployed in cabin. ATC was easy to work with.  High speed direct for the ILS XX into ZZZZ.  Captain continued to coordinate with the F/A's and a call to Dispatch.  Landed [safely] in ZZZZ and taxied to a hard stand.  Approximately 40 miles out I called ZZZZ Ops and confirmed they knew we were inbound.


Synopsis: B787 flight crew reported a loss of cabin pressurization during climb that caused lingering fumes from the overheated left Pack. Flight crew coordinated with ATC for an expedited air return which concluded in a safe landing.