Karine DelafosseOctober 19, 2022
The Federal Aviation Administration is investigating the cause of mysterious GPS interference that has shut down a runway at Dallas-Fort Worth International Airport in recent days and caused some planes in the area to be diverted to areas where the signals were working properly.
The disruption first became known on Monday afternoon when the FAA issued a report through ATIS (Automatic Terminal Information Service). It warned flight crew and air traffic controllers of GPS interference over 40 miles of airspace near Dallas-Fort Worth Airport. The notice read in part: “ATTN ALL AIRCRAFT. GPS REPORTED AS UNRELIABLE WITHIN 40NM BY DFW.”
A dramatic effect
An Advisory issued around the same time by the Air Traffic Control System Command Center reported that the region has been experiencing “GPS anomalies that are dramatically affecting flights to and from Dallas-Fort Worth and neighboring airports.” It goes on to say that some of the airports rely on the use of navigation systems that are older than GPS.
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Gpsjam.org, a website that monitors GPS jamming in real time, published this map showing the specific areas where planes were reporting unreliable GPS.
John Wiseman, the operator of GPSjam.org, said on Twitter that the disturbance appeared to begin around 1:00 p.m. local time and increased over the next few hours. He provided a time-lapse video that illustrates what he was talking about.
A day later, Wiseman reported that it wasn’t just about the disorder continuing, but that aircraft on the ground in the affected region were also unable to obtain reliable GPS readings. In addition, fine-grain tracking of the disturbances suggested that military operations — the most common source of unintended disturbances — played no part. A few hours later the unresolved problems not just continued but had spread to areas near Waco.
As mysterious as it began, it ends
Then, around 11:00 p.m. Dallas time, the disruption ended. As mysterious as the disturbance had started, it had stopped. In an online interview, Wiseman wrote:
This GPS interference was noticeable because it was significant, covered a relatively large area, and did not look like the typical interference I see in the United States, which is almost always clearly associated with military testing or training in a military theater of operations. My understanding is that a lack of GPS is not an aircraft emergency, but it can definitely be annoying and lead to delays and even canceled flights. I don’t know what caused this interference or if it was intentional, but it almost certainly came from an electronic device and not a natural phenomenon. GPS is an odd part of the world’s infrastructure as it is so important but also very easy to breach through intentional or accidental jamming. I hope it stays usable!
Civilian GPS is based on low-power satellite signals broadcast in the L-band, a radio frequency range also used by civil terrestrial radio sources, including 5G mobile devices. This makes GPS vulnerable to unintentional interference from the introduction of this next-generation technology. Devices used on military bases are also a common cause.
However, when unintended disruptions occur, authorities can usually pinpoint the cause within hours. On Wednesday, FAA officials said in a statement, “The FAA is investigating reports of problems with GPS-guided approaches for one of the runways at Dallas-Fort Worth International Airport. The agency has found no evidence of intentional interference and is working to determine the cause. Airplanes can land safely on other runways.”
With no known cause, experts can only speculate.
“We do not know if there are malicious actors behind this incident or if it is the result of interference,” said Josh Lospinoso, co-founder and CEO of aircraft and transportation security company Shift5 and a former US Cyber Command official, in an interview. “Interference is a hot topic for airports and airlines right now. A few months ago there was a big push by wireless carriers to roll out 5G at airports, which was a terrible idea considering how many legacy devices on airplanes rely on the wireless bands that 5G is handicapping.”
Lospinoso also noted the vulnerability of civilian GPS to intentional spoofing and jamming. North Korea used GPS jamming in 2012. Three years ago, the Center for Advanced Defense Studies reported that Russia was conducting extensive spoofing of signals used by GPS and other global navigation satellite systems in Syria and other combat zones.
Other forms of aircraft navigation are similarly vulnerable. For example, in 2012, researcher Brad Haines reported that he was able to spoof the ADS-B signals that an aircraft with surveillance technology relies on to determine its position via satellite navigation. The researcher demonstrated how attackers could use these fake signals to create “ghost planes” that would appear on air traffic controllers’ screens. Researchers have also developed a low-cost hack that spoofs the instrument landing systems that planes rely on to land safely.
This week’s event is similar to one held in Denver last January, according to GPSWorld. In the January episode, planes in 50 nautical miles of airspace around the airport reported unreliable GPS for more than 33 hours.
Readers should know that GPS interference is not life threatening. But as mentioned, episodes like this cause cancellations, delays, and other inconveniences. More importantly, they underscore the vulnerability of a system the world is increasingly reliant on. More worrying than the disorder itself is the mystery of what caused it.