Date: 202103
Local time of day: 0601-1200
Location: ZAB.ARTCC, NM
Flight conditions: VMC
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Cruise
Airspace: Class A ZAB
ATC / advisory: Center ZAB
Reporter organization: Air Carrier
Reporter function: Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Human factors: Confusion; Distraction; Troubleshooting; Fatigue; Human-Machine Interface
Anomaly: Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Ground Equipment Issue
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Became Reoriented; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: ATC Equipment / Nav Facility / Buildings; Software and Automation; Company Policy
Primary problem: ATC Equipment / Nav Facility / Buildings

Narrative: Somewhere after Burns Flat (BFV) at 38;000 ft. and until ZUN VOR; we had encountered first an ATC Fault EICAS message. Oddly then on both transponders. First Officer was the Pilot Flying. So; we discussed and went into the QRH and complied. I had then though to ask ABQ ARTCC if they were able to see us on their radar scope. The controller had replied yes. So when I remarked of our issue; he knew right away that jamming was taking place. Now I didn't clarify if this was any kind of military exercise and if this was normal. He acted as though it was. Shortly after this; we started slowly seeing other EICAS messages. I can't remember the exact order though. I believe the next was EGPWS TERR or so. Then L GPS appeared not too far after this. Maybe R GPS as well; maybe. Eventually we saw UNABLE RNP. So we definitely knew GPS jamming was making sense. The RNP ANP scales on the Pilot Flying Display bottom was like RNP 2.00 ANP 2.93 in amber color. It was clear our GPS was in an inertial mode. I did select radio updating eventually per the QRH's procedural instructions. Center never seem too concerned as nothing else was said. The weather was quite good and while concerned; I had a good idea as we made our way towards ZZZ1; the start of the RNAV star; the GPS navigation would probably return to a normal state and it did. There wasn't any flight safety breaches or traffics conflicts as this event happened entered at cruise. Although; I did forget to make a maintenance log entry required by mandatory reports. I may have been more fatigued than I was aware. Sleep was fragmented in chunks of multiple 2 to 3 or so hrs. on this day. Intentional GPS jamming I suppose. I've never encountered this in my entire career here. Wondering if the military does these exercises; but I would expect we'd be notified via a NOTAM and on our [flight plan] if it was known. I suppose if we knew we could of had a different routing? I don't believe compromised safety as in this case was an issue. It never degraded to a more severe off course deviation and didn't cause traffic conflicts. Don't get me wrong we were concerned and a bit miffed. I will file a security report and read more on the subject of GPS jamming interference's.




Synopsis: An air carrier pilot reported GPS jamming.