A lot of talk about GPS hacking/spoofing taking down (civilian) aircraft s False. (I cannot comment on high tech mil systems, but mil aircraft still use what I am about to explain).
Aircraft don't use GPS. At least not as their main nav systems. There are two sets of flight Rules, Visual Flight Rules where pilots are trained to use charts that have terrain objects as references, such as rivers, towers and other landmarks (this is what Kennedy was apparently flying as he was not instrument rated).
And Instrument Flight Rules, where pilots use VHF Omni Range (VOR) and Distance Marker Equipment (DME). Flight paths are defined by radial to and from VORs and DMEs. These systems provide a distance and a bearing. Using two allows you to work out your location.
IFR Pilots don't use GPS. Yes, many aircraft now have GPS but it's for location services not for navigation.
GPS is mostly used 1) to back up the already backed up VOR1/VOR2 DME1/DME2 equipment and to find your parking space at the airport.
Notwithstanding, some civilian pilots will use GPS for ease, for if you're instrument rated, a loss of GPS will merely tell you-you're in the wrong place. It won't bring down a plane.