Large Transport; Low Wing; 2 Turbojet Eng
Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Workload; Human-Machine Interface
Aircraft Equipment Problem Less Severe
Air Traffic Control Provided Assistance; Aircraft Equipment Problem Dissipated; Flight Crew Overcame Equipment Problem; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Became Reoriented
ATC Equipment / Nav Facility / Buildings; Airspace Structure; Software and Automation; Aircraft
As we were en-route at cruise altitude FL360 feet 80 miles northwest of HMN VOR when we started to experience degraded navigation performance in the form of ATC fail alerts and an increasing ANP (Actual Navigation Performance) number relative to RNP (Required Navigation Performance). We notified ATC and were informed of GPS jamming somewhere north of El Paso. As we proceeded west; the navigation performance of our aircraft degraded more to the point where we received an UNABLE RNP message along with a GPS amber message. Once we got west of ELP and the TCS area; the navigation performance gradually improved and came back within normal parameters. Route track and actual position of aircraft were unaffected and there were no deviations from the planned and cleared routing. Not really any way to avoid other than don't jam GPS. But considering ATC was aware of it and able to keep aircraft notified of where and when the jamming effects would abate; it is not a huge hazard.
Captain reported experiencing GPS Jamming; which rendered RNP (Required Navigation Performance) unavailable.