These spoofing attacks "come from powerful electronic-warfare transmitters in Russia, Ukraine and Israel," University of Texas at Austin aerospace engineer Todd Humphreys told WSJ. The attacks aren't directed at civilian planes, but those planes do get in the way.
In one instance where this happened, a United Airlines flight headed from Delhi to the East Coast of the US "picked up a spoofed GPS signal" over the Black Sea, south of Ukraine, which "caused problems for the rest of the flight."
Another occurrence saw a private Embraer jet almost fly into the hostile airspace of Iran without clearance, which could have been extremely dangerous had it not been corrected in time. Another flight, a Boeing 787, had to abort two landings, "one of them 50 feet above the ground, after the loss of a GPS signal kicked off a series of instrument problems."
Detailing the circumstances of the spoof, the Wall Street Journal reports that "At first, the flight appeared to follow the same GPS track that previous flights took across Asia toward their scheduled destination at Newark Liberty International Airport." The equipment was unable to reset, and even after the aircraft flew past the area where the "spoof" was, the coordinates continued to drift. Alternate navigation systems in place aided the aircraft in getting safely to its destination.
Other instances of "spoofing" have resulted in false readings, causing the safety system to advise pilots to "pull up." This can lead to pilots doing so unnecessarily. False time and position data resulting from "spoofed" signals can cause problems for pilot messaging services.
"Aviation-safety officials said spoofing has disrupted some flights but hasn’t posed major safety risks," the Wall Street Journal reports. "While pilots are trained on how to use non-GPS navigation systems as a backup, managing the bogus GPS signals and alerts risks dividing pilots’ attention if a more serious problem strikes."
Officials in aviation are working on plans to "harden" civilian aircraft so that they won't be susceptible to these kinds of attacks, but that kind of technology won't be available until at least next year.