There are two different things:
One is GPS jamming while the other is GPS Spoofing.
Jamming: GPS won’t work or it will work with a strange behavior (recognized by the pilot), it could even lose GPS signal. Easy to perform. https://theaviationist.com/2018/02/05/see-how-usaf-aggressors-jam-civilian-gps-signals-in-training-at-nellis-air-force-base/
Spoofing: GPS equipment will obtain “valid but false” data. If the a/c is not redundant with a Hybrid solution, i.e. IRS, or with an integrity or RAIM function, the pilot may not appreciate this false data. This is hard to perform and it’s suffered in a small radius around the emitter (20NM approx.)
The FAA has implemented a “stop buzzer” emergency phrase to stop the US jamming test if a pilot gets into trouble in flight – here.
No such option in Europe…
It is nice to have a phrase for that – but what is the guaranteed service level of the US forces from mentioning that phrase to actually stopping the jamming?
I can imagine it takes significant time from the ATC unit along the chain of command (who in the military can actually decide to stop such a test) until the guy at the button can actually shut it down – if there is any such procedure defined at all …
For me that sounds more like an FAA placebo than something of real value for flight safety.
“Larnaca could become an absolute shitshow when the Americans jammed it”
How do they know who does the jamming?