A strong transmitter on the GNSS band drowns the weak satellite signal and the cockpit goes from precision to 'GPS unreliable.' The map may blank. The approach may degrade. The pilot knows something is wrong because the system complains. Spoofing is a lie. A ground emitter broadcasts a counterfeit satellite message that the receiver accepts as authentic. The flight-management computer can decide the aircraft is miles from where it is. The clock can jump. Terrain alerts can fire over flat ground. ADS-B can report a false position to air traffic control. EASA is blunt about the ranking. Spoofing is harder to detect and can poison several systems at once. That is why business-aviation operators are rewriting procedures this year rather than treating interference as a military curiosity over someone else’s war. An AIN roundtable this week put the same problem on the bizjet agenda. Honeywell and the manufacturers are no longer selling only prettier maps. They are selling how to fly when the map is lying.
The FAA’s GNSS Interference Resource Guide 1.1, issued in March after an industry-government action team rewrote the first edition, names the neighbourhoods. Eastern Mediterranean. Black Sea. Russia and the Baltic. India-Pakistan border. Iraq and Iran. Korea. Areas around Beijing. IATA data already showed GNSS-loss rates climbing sharply; spoofing reports rose faster still. A British defence minister’s jet once painted itself over St Petersburg while it was still in the Baltic. Crews report the aircraft “jumping” hundreds of miles on the display. That is not a comms glitch. It is a navigation integrity failure. The answer in the cockpit is not more GPS. It is disbelief. Inertial reference units keep a position that drifts slowly but does not teleport. VOR, DME and ILS do not care what a fake satellite says. DME-DME cross-fixes still work where the ground navaids survive. Radio-magnetic bearings and ATC radar still exist if someone is looking. The procedure is crude and old. Cross-check the FMS against raw navaids. Watch the clock. If time jumps, treat GNSS as contaminated. Disconnect the approach that depends on it. Tell the controller in plain words that the box is lying. EASA’s July 2026 SIB update finally gives phraseology for that conversation and tells ANSPs to keep enough conventional capacity when the satellites cannot be trusted. Dispatch is supposed to brief the corridor before start-up, not after the first terrain warning. Training only counts if the simulator can spoof, not merely fail, the GPS.
India is not on the edge of this map. It is on it. The FAA list includes the India-Pakistan border. Parliamentary figures cited in 2026 put thousands of airline interference reports on the books, with the monthly average jumping by more than 200 percent into early this year. DGCA circulars already demand reporting. AAI works with the Wireless Monitoring Organisation. Pilots on Amritsar, Jammu and some Gulf and Southeast Asia tracks have described interference as routine. In November 2025, spoofing over the Delhi FIR arrived without a useful NOTAM. An Air India Delhi-Amritsar flight in June briefly entered Pakistani airspace during a hold and go-around. Investigators will separate crew action from signal lies. The operational lesson does not wait for the file. A false position near a closed, militarised border is not an inconvenience. It is an airspace violation with two air forces underneath it. Business jets that file flexible routes through West Asia, the Black Sea and the Himalayan approaches face the same physics with thinner crews and less airline operations-centre backup. Asian operators who still treat GNSS as gospel are flying last decade’s assumption. The ones who will last treat it as one sensor among several, keep inertial and ground navaids alive, train for the lie rather than the blank screen, and tell ATC the moment the picture stops matching the world. Losing GPS is recoverable. Believing a fake GPS is how a well-maintained aircraft ends up in the wrong country.