GNSS Spoofing: When Navigation Information Cannot Be Trusted

GNSS spoofing is no longer a theoretical concern confined to military operations. Flight crews are increasingly encountering false satellite signals that can cause an aircraft’s navigation systems to calculate a convincing—but incorrect—position. Unlike jamming, which normally produces an obvious loss of signal, spoofing may initially present information that appears completely valid.

The first indication may be a sudden map shift, disagreement between raw data and the flight management system, abnormal groundspeed or wind information, incorrect time, unexpected terrain or airspace warnings, or a position that does not correspond with conventional navigation aids. During approach, departure, or operations near conflict areas, the resulting distraction and increased workload can quickly become a significant threat.

The essential defence is disciplined cross-checking. Crews should compare GNSS-derived information with all available independent sources, including DME, VOR, IRS position, radio altimeter indications, ATC information and visual references. If spoofing is suspected, pilots should avoid making abrupt flight-path changes based solely on one indication. Maintain aircraft control, confirm the actual position, apply the relevant QRH or company procedure, and advise ATC using clear, unambiguous language.

Good crew resource management is critical. One pilot must remain focused on flight-path control while the other diagnoses the problem, verifies navigation accuracy and communicates with ATC. Automation should be used only while it remains trustworthy; crews must be prepared to revert to an appropriate lower level of automation.

Pre-flight threat assessment should include NOTAMs, company advisories, expected interference areas, available conventional navigation coverage and suitable contingencies. Any suspected event should be reported promptly and accurately before another crew encounters the same threat.

The message for crews is simple: a navigation display can be precise without being correct. Trust must be earned through continuous cross-checking, sound judgement and disciplined application of basic flying skills.