Date: 201910
Local time of day: 0001-0600
Location: EGGX.ARTCC, FO
Flight conditions: IMC
Aircraft: B767 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Reporter organization: Air Carrier
Reporter function: Pilot Flying; First Officer
Reporter qualification: Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Human factors: Distraction; Situational Awareness; Fatigue
Second reporter function: Relief Pilot; Pilot Flying
Anomaly: Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Returned To Clearance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Became Reoriented
Contributing factors: Weather; Human Factors
Primary problem: Human Factors

Narrative: On the long-delayed flight our crew experienced an altitude deviation while on a random route in Oceanic Airspace. Backing up in time to what I believe is a major contributing factor to the event; the crew desk apparently attempted to call our rooms multiple times in the very early morning hours in an attempt to reset our rest. I did not answer my phone until my scheduled wakeup time around 9 am local; at which time the crew desk informed me that my rest had been 'reset'. I was now wide awake; and unable to obtain additional rest that day before reporting for duty. Next; at the airport we encountered a weight-limited takeoff; requiring departure from an unfamiliar runway and associated SID adding to our workload; but we briefed as a team; and agreed that this flight's very late departure would be a threat we would manage together by taking our time. In spite of what we considered an irregular operation; the Captain led the crew effectively at all times; encouraging input; not rushing and using all resources to ensure a safe departure. The IRO was extremely helpful during the busy preflight; pushback; taxi and departure. The flight continued uneventfully until the altitude deviation; which occurred in an attempt to escape continuous moderate turbulence.Though not on the flight deck at the time of the deviation as I was on my scheduled rest break; I believe that this event's genesis can be traced back to the multiple phone calls each crew member received which I believe was in clear violation of the FAA's 'one-phone call policy'. The Crew Desk attempted to reach each of us in the very early morning hours that day to attempt a 'soft reset'. The flight was eventually delayed over 8 hours to show a 'legal' 10-hour rest reset; but effectively this ended up being an extremely long duty day; as I was unable to get additional rest after those calls. At report time however; I certified 'Fit for Duty'; as I felt ready; awake and alert (but perhaps unable to effectively assess how I would feel 11 hours later). I believe that this insidious effect of interrupted sleep on our collective decision-making abilities was a major contributing factor in the error the Pilot Flying and Pilot Monitoring made many hours later.


Second narrative: This was simply an altitude deviation due to wishful thinking because of our immediate circumstance. The Captain and I both thought we saw a clearance to FL330 because that's what we wanted to see. At the time we were in heavy turbulence. There were many things that lead to our error.For me it started with something I ate the night before. That evening I went to bed based on a 10am van time for the return flight. During the night the phone rang several times waking me. The phone also rang right at wake up time which I answered and was informed about an 8 hour delay. I then went to breakfast where I started feeling the effects of food poisoning. I went back to my room and tried to sleep. After a few hours I was able to get out of the room for medication. I decided I would wait until 1630 local time to decide the need to call in sick. At 1600 I vomited and I immediately began to feel better. I was also able to nap until my wake up time 1730. At van time I informed the other flight deck crew members that I had been sick but felt better and was able to fly.I participated in all flight deck preparations; taxi; and takeoff procedures required of the IRO. I was on first break that lasted 3hrs+ 8min. Once back on the flight deck I took over the flying pilot duties. We got into a heavy area of turbulence. After the turbulence did not seem to be improving (the Captain had seated the Flight Attendants) we decided to request a higher altitude from ATC. They denied our 34;000 ft. request so we immediately sent another request for 33;000 ft. The Captain and I both thought we saw a clearance to 33;000 ft. At the time we were in very turbulent air. After we started the climb I checked CPDLC to make sure report was armed. When I couldn't find the report prompt I realized our mistake and informed the Captain. By that time we received a call from ATC. We descended back to 32;000 ft. ATC sent a CPDLC message in regards to our altitude. We were off our assigned altitude for about 3 minutes. We did not get any traffic resolutions or TCAS alerts. 20 minutes later we received a message 'when can you accept FL340'. But the worst of the turbulence was over by then. Fatigue was definitely a factor in this error.


Synopsis: B767 flight crew reported experiencing fatigue that resulted in an altitude deviation during cruise.