On 21 September the Government Accountability Office published GAO-26-108439. It looked at eight spectrum-dependent systems the FAA uses to talk to aircraft. Formal risk assessments covering spoofing, jamming and other spectrum attacks were complete for one of them. The agency, the auditors said, still lacked a defined real-time way to watch those threats across the National Airspace System. Nine recommendations followed like finish the risk papers, monitor continuously, tighten authentication on ACARS and CPDLC so a false message is harder to insert. The Department of Transportation, speaking for the FAA, agreed with all nine. None of that is a finding that a particular flight was spoofed yesterday. It is a finding that the infrastructure which airlines treat as background can be lied to.
Airline cockpits have several ways of knowing where they are. There are inertial units, radio navaids, GPS, a dispatcher and a controller who can still see a primary return if the transponder is believed. Many general-aviation aircraft have a panel-mount GPS, a portable tablet and the pilot’s eyes. When the satellite picture is jammed, the position freeze or the 'GPS lost' flag is at least honest. Spoofing is ruder. The box keeps looking healthy while the aircraft icon slides toward a place the aeroplane is not. Heading, groundspeed and even the clock can drift. A coupled autopilot will follow the lie if nobody notices the raw instruments disagreeing.
What a pilot does then is old-fashioned. Cross-check the magnetic compass and the attitude indicator. Ask whether the DME, VOR or a visual fix matches the magenta line. Tell ATC that GNSS is unusable and fly the clearance they can issue without it. Do not chase a rapidly wandering track. Emergency-services and medevac operators who work near known interference like conflict zones, some coasts, some test ranges already brief this. The rest of the fleet meets it as a surprise.
The GAO paper is mostly about ground and air-ground links, not a Cessna’s Garmin. The practical overlap is the same physics. Spectrum that is not authenticated can be copied. A tablet that is the only moving map in the cockpit is a single point of failure dressed as convenience. Until the FAA can see spoofing as it happens, the last check remains the one the instrument instructor already teaches: if two sources disagree, believe the one that does not need a satellite.