Date: 202101
Local time of day: 1801-2400
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Weather elements / visibility: 5
Light: Night
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Human factors: Physiological - Other; Fatigue; Situational Awareness
Second reporter function: First Officer; Pilot Flying
Anomaly: Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Air Traffic Control; Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented
Contributing factors: Environment - Non Weather Related; Human Factors
Primary problem: Human Factors

Narrative: While operating our flight from ZZZ to ZZZ1 I was the Pilot Monitoring. At the time of the event; I was eating my catering and the Pilot Flying and I both found it easier for the PF to respond to ATC and manipulate the FMS. At some point at cruise altitude; ATC cleared us to fly direct from present position to 'ZZZZZ.' The PF responded to ATC and erroneously typed 'ZZZZZ1' into the FMS scratchpad and entered the waypoint as the direct-to navigation fix after both pilots checked the resulting dashed 'proposed course line' on the PF's ND screen. After several minutes; ATC inquired if we were proceeding direct to 'ZZZZZ' as he showed us drifting right of the intended course. This alerted us to double-check our navigation and to discover that we were navigating to the wrong fix; the misspelled 'ZZZZZ1.' The PF corrected the spelling of the assigned waypoint in the FMS; proceeded direct to 'ZZZZZ' and explained our error to ATC.I can identify three things that might have prevented this event: 1) The normal procedure and best course of action would have been for the Pilot Monitoring to stop eating; respond to ATC and manipulate the FMS. I do not; however; think this was much of a contributing factor. The PF is a 'strong' and extremely competent pilot highly experienced on the aircraft. I don't think the PF's assumption of those duties was particularly taxing/burdensome to the PF as we were in cruise at a very quiet and low-threat portion of the flight. It is not unusual for a PF to respond to ATC and manipulate the radios and FMS while a PM is eating. I have always personally tried to not touch anything other than my food while eating in the aircraft and think this is an especially important practice during the current health pandemic. While I could have sanitized my hands once I completed the radio calls and navigation tasks; it was more convenient to allow the PF to perform those duties for me. 2) The best course of action would have been for the PF to scroll the flight plan and chosen the assigned Direct-To waypoint 'ZZZZZ' from the flight plan. However; the aircraft's FMS is slow to respond; making scrolling through a long flight plan somewhat laborious; tempting one to effect the change via the scratch pad method. The PF alternatively could have checked the paper copy of the flight plan for the correct spelling of the waypoint before typing it into the scratch pad. 3) I had the 'PROG' page selected on my FMC and did notice that the course to the incorrect 'ZZZZZ' was almost 25 degrees to the right of the bearing of ZZZ1 and thought it odd to be navigating that far off the bearing to destination. This matched my curiosity about the dashed 'proposed course line' displayed on the PF's ND when the erroneous fix was entered into the scratch pad. However; knowing that the destination was more than 1200 miles away at the time; I assumed there was a significant 'bend' in the original flight plan. Had I mentioned my observation to the PF; it might have cued the PF to check the spelling of the waypoint as the PF made the entry from an assumed spelling. When checking off frequency with the controller who made the direct-to assignment; the PF apologized for the error and asked if we should contact anyone for further discussion/explanation. The Controller indicated that he did not believe that would be necessary.My time-in-type; time-in-position and total-time are not readily available and I don't want to delay submission of this report in order to track down those numbers. I therefore entered a generic '1' in each of those blocks in the report.  Each of the numbers actually totals in the thousands. Fatigue was somewhat of a factor in the event. It was the last duty day of a pairing that had us flying a mix of long and short legs; including international legs to and from an international country; and crossing the country and multiple time zones. We shifted between flying and non-flying duty periods several times and scheduled rest varied from long to short periods. Obtaining 'quality' rest was a challenge and I most definitely accumulated a sleep deficit by the day/time of the event. I estimate that I slept a total of 5.5 hours during the rest period prior to the duty period of the event; one sleep period of 4 hours and another nap of 1.5 hours; waking approximately 3 hours prior to reporting for the event duty period.


Second narrative: First; I can't confirm all the information requested above.  I don't remember exactly which Center we were talking to or pinpoint where we were relative to a fix.  I think we were with ZZZ but it might have been ZZZ1; and we were south of ZZZ1 and west of ZZZ2 at the time; going direct to ZZZ2. I was the FO and the Pilot Flying. We were cleared direct to ZZZZZ. The Captain/PM was eating his catering so I was also answering the radio. When we received the clearance to ZZZZZ it was easier for me to enter the fix in the FMC than it would have been for him; so I typed that in.  About 10-15 minutes later the Controller said that he showed us about 45 degrees off course and asked whether we were going direct to ZZZZZ as cleared. We double-checked for NAV selected to the fix; looked at the course deviation; and checked the FMC; and they all confirmed direct ZZZZZ. On closer examination; though; we realized that we were actually going to a fix called ZZZZZ1; and that I had misspelled the correct fix when I typed it in. I didn't select it from the fixes listed on the flight plan; and should have done that instead of typing it in. That would have obviated the error. The aircraft made a fairly significant turn to the right when I executed the direct-to command and I thought at the time that if I'd known it was such a big difference in the track I'd have requested direct sooner. The Captain later said that he'd thought it was strange that the bearing/distance on the FMC didn't match what the airplane had turned to when we made the turn; and wished that he had said something at the time so that we could resolve the discrepancy.  I should have caught the misspelling at the time; but I also should have selected the fix from the list instead of typing it in. I indicated that fatigue was a factor with this event because I think I would have caught the error or not made it in the first place. We overfly ZZZZZ often and I've noticed the variant spelling before. It was the last night of the trip; though; and I'd not had more than 4 consecutive hours of sleep (or more than 5.5 total) on any of the previous days.


Synopsis: Air Carrier flight crew reported a heading deviation caused by not following SOP's and a change to the crew's normal procedures due to the pandemic.