Aviation's GPS backup systems exist but fall short of true resilience, analysts warn

Irish Torres, an aerospace technology writer at Safran Navigation & Timing, argues that GPS resilience in aviation has largely been treated as a compliance checkbox instead of a design priority, even as interference incidents grow more frequent and widespread. She identifies jamming and spoofing as the two principal threats to GPS.

The U.S. Federal Aviation Administration (FAA) warns that GPS is subject to both intentional and unintentional interference and advises pilots to be prepared to navigate without satellite-based systems. For many commercial operators conducting IFR operations, the FAA explicitly requires retained navigation capability independent of GPS, covering DME/DME, inertial reference units and VORs for en route and terminal operations, plus VOR and ILS capability for final approaches. The FAA also maintains a VOR Minimum Operational Network (VOR MON), a reversionary capability during GPS disruptions designed so aircraft operating within the continental United States can reach an airport with a non-GPS instrument approach using conventional navigation aids.

The FAA acknowledges that using VOR MON during an outage can involve more circuitous routes than GPS-enabled RNAV operations, increasing workload for pilots and air traffic controllers and potentially causing delays and higher fuel consumption. The International Civil Aviation Organisation (ICAO) has developed a roadmap addressing GNSS radio-frequency interference, with immediate steps including support for safe continuation of flight operations during interference through contingency plans and heightened crew and controller awareness. ICAO's longer-term approach calls for greater resilience through technological improvements to satellite navigation, independent timing sources, and complementary positioning, navigation and timing capabilities.

This case illustrates a broader pattern in safety-critical infrastructure: a backup system can satisfy a regulatory checklist while still failing a resilience test, because the two questions are not the same. Aviation's non-GPS navigation aids were built for an earlier era, and their continued presence in the rulebook does not by itself confirm they remain funded, trained-for and integrated at the level today's traffic assumes.

Torres frames the real test as whether independent capability, spanning DME, inertial systems, VOR and ILS, can absorb repeated or geographically widespread disruptions, not just a single outage. VOR MON exists precisely for this scenario, but the FAA's own acknowledgment that it adds circuitous routing, controller workload, delay and fuel burn shows that the backup carries a real operating cost even when it works as designed.

What remains to watch is whether ICAO's longer-term roadmap, covering satellite navigation upgrades, independent timing sources and complementary PNT capabilities, translates into sustained investment in the ground infrastructure and crew training that VOR MON depends on, or whether that infrastructure keeps eroding as the industry designs around GPS availability by default.