GPS interference caused the FAA to divert air traffic in Texas. Experts stunned

The Federal Aviation Administration is investigating the cause of mysterious GPS interference in recent days that closed a runway at Dallas-Fort Worth International Airport and forced some planes in the region to be diverted to areas where signals were working properly.

The outage first came to light Monday afternoon when the FAA issued an advisory on ATIS (Automatic Terminal Information Service). It warned flight crews and air traffic controllers of GPS interference over a 40-mile swath of airspace near the Dallas-Fort Worth airport. The advice read in part: “ATTN ALL AIRCRAFT. GPS UNRELIABLE REPORTED WITHIN 40NM OF DFW.”

A dramatic impact

An advisory issued around the same time by the Air Traffic Control System Command Center, meanwhile, reported that the region was experiencing “GPS anomalies that dramatically impact” flights to and from Dallas-Fort Worth and neighboring airports. It went on to say that some airports relied on the use of navigation systems older than GPS.

Gpsjam.org, a website that monitors GPS interference in real time, published this map showing the specific areas where planes reported unreliable GPS.

John Wiseman, the administrator of GPSjam.org, said on Twitter that the interference appeared to start around 1 p.m. local time and increase over the next few hours. He provided a time-lapse video that illustrates what he was talking about.

A day later, Wiseman reported that not only the interference Get on, but that aircraft on the ground in the affected area were also unable to receive reliable GPS readings. In addition, the fine-grained tracking of the interference suggested that military operations — the most common source of unintended interference — played no role. A few hours later, the unexplained problems not just sequel but had spread to areas near Waco.

As mysterious as it started, it stops

Then, around 11 p.m. Dallas time, the interference ended. As mysteriously as the interference started, it had stopped. In an online interview, Wiseman wrote:

This GPS interference stood out because it was significant, covered a relatively large area, and didn’t 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 area of ​​operations. It is my understanding that the lack of GPS is not an aircraft emergency, but it can certainly 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 a piece of electronic equipment and not a natural phenomenon. GPS is a bit of a weird part of the world infrastructure because it’s so important, but also very easy to break, either intentionally or accidentally. I hope it continues to be useful!

Civilian GPS relies on low-power satellite signals broadcast in the L-band, a radio frequency range also used by civilian terrestrial radio sources, including 5G mobile devices. That makes GPS susceptible to accidental interference from the rollout of this next-generation technology. Equipment used on military bases is also a common cause.

However, when unintended interference occurs, authorities can usually locate the cause within a few hours. On Wednesday, FAA officials said in a statement: “The FAA is investigating reports of problems with GPS-guided approaches to one of the Dallas-Fort Worth International Airport runways. The agency has found no evidence of intentional interference and is working to identify the cause. Aircraft can land safely on other runways.”

With no known cause, experts can only speculate.

“We don’t know if there are malicious actors behind this incident, or if it is the result of interference,” Josh Lospinoso, co-founder and CEO of aircraft and transportation security company Shift5 and a former US Cyber ​​Command official, said in a statement. an interview. “Interference is a current issue for airports and airlines right now. A few months ago, there was a lot of pressure from wireless carriers to roll out 5G in airports, which was a terrible idea from the perspective of how many legacy devices on airplanes depend on the wireless bands hampered by 5G.

Lospinoso also pointed to the susceptibility of civilian GPS to intentional spoofing and jamming. North Korea took advantage of GPS jamming in 2012. Three years ago, the Center for Advanced Defense Studies reported that Russia had conducted 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 also vulnerable. For example, in 2012, researcher Brad Haines reported that he was able to falsify the ADS-B signals that aircraft with surveillance technology rely on to determine their position via satellite navigation. The researcher showed how attackers could use these forged signals to create “ghost planes” that would appear on air traffic controllers’ screens. Researchers have also devised a cheap hack that fakes the instrument landing systems that airplanes rely on to land safely.

This week’s event is similar to the event that took place 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 noted, episodes like this do cause cancellations, delays, and other inconveniences. More importantly, they underscore the fragility of a system on which the world is increasingly dependent. More worrisome than the interference itself is the mystery of what caused it.