Preparing for GNSS Interference During Routine Flight Operations

Article originally published on SM4

What was once considered a threat confined largely to conflict zones has become an increasingly common operational hazard for pilots in the United States. As Global Navigation Satellite System (GNSS) interference continues to increase both within and near U.S. airspace, domestic flight crews must remain vigilant and prepared to recognize and safely manage extended periods of interference.  

Over the past several decades, GNSS has evolved from a convenience to a critical component of modern aviation safety. Today’s aircraft rely on GNSS for aircraft positioning and navigation, instrument approaches, surveillance and traffic awareness, terrain awareness, and runway overrun prevention. When GNSS signals are disrupted—whether by intentional interference or unintentional causes—aircraft must transition to alternative, often less capable, navigation systems to safely continue flight operations. 

GNSS interference generally occurs in one of two forms: 

• Jamming – A signal that inhibits a GNSS receiver from acquiring the intended satellite signal 
• Spoofing – A false signal designed to imitate an authentic GNSS signal while providing inaccurate positioning and navigation information 

According to the International Air Transport Association (IATA), the global rate of GNSS signal loss per 1,000 flights increased 65% in the first half of 2024, compared to the same period in 2023. In June of 2025, the Federal Aviation Administration (FAA) reported an average of 900 daily global spoofing reports. 

While the majority of GNSS interference continues to occur in and around global conflict zones, reports of disruptions are becoming increasingly common during routine flight operations in the United States. Even when interference is unintentional, these events can have significant operational and safety implications. 

On May 14, 2026, a King Air C90 was involved in a fatal accident while on approach to Ruidoso, New Mexico. The Preliminary Report from the National Transportation Safety Board (NTSB) stated that “GPS jamming activities that encompassed the area around the accident were being conducted by the United States military during the time of the flight.” 

Although the preliminary report does not establish the extent to which GPS jamming may have contributed to the accident, the event serves as a sobering reminder that GNSS interference is no longer a distant concern and should be treated as a credible operational risk. 

In March of 2026,  the FAA Flight Technologies and Procedures Division (AFS-400) released an updated resource guide warning U.S. operators and pilots that GNSS interference is becoming more frequent, widespread, and persistent. 

The FAA identifies several potential sources of interference within the United States. The most common causes are military testing and training activities, though interference may also result from law enforcement efforts to counter unauthorized drone operations, naturally occurring phenomena such as solar activity, or from intentional disruption by malicious actors. 

As part of mission planning, flight crews should prepare for the possibility of GNSS interference by assessing associated operational risks and incorporating mitigation strategies and contingency procedures into the formal preflight briefing. Before each flight, pilots should review GPS NOTAMs to identify any planned GNSS interference activities along the route of flight. It is important to recognize that some military GPS interference exercises can affect aircraft operations up to 400 nautical miles from the source. 

Pilots should also be able to recognize the indications of both GNSS jamming and spoofing and be familiar with the aircraft manufacturer’s guidance for operating in environments where GNSS signals may be degraded or unavailable. 

During flight, maintaining situational awareness is essential. Pilots should remain vigilant by maintaining the minimum safe altitude outside of takeoff and landing, continuously cross-checking GNSS-derived navigation information with independent navigation sources such as ground-based navigation aids and inertial reference systems, and promptly notifying ATC if GNSS performance degrades or signal integrity is lost.  

When operating in areas where GNSS interference has been reported, pilots should use ground-based instrument approaches whenever practical and identify nearby Minimum Operational Network (MON) airports as potential alternate navigation and approach options. 

GNSS interference can occur anywhere, at any time, and at any altitude. Staying prepared, recognizing interference early, and reporting GPS anomalies after flight are essential to maintaining the safety and integrity of our airspace.

Training for the Moments That Matter Most

The Los Angeles Police Department’s (LAPD) Air Support Division (ASD) is the largest municipal airborne law enforcement unit in the country. With a fleet of 16 helicopters and more than 50 pilots logging approximately 17,000 flight hours each year, the division provides critical support from above across Los Angeles’ 435 square miles. 

“We always have two aircraft in the air, no matter what,” said former LAPD Chief Pilot Kevin Gallagher. “It’s a police car in the sky—searching for crime and responding to calls just like officers would on the street.” 

For more than two decades, LAPD has trusted FlightSafety to prepare its pilots for the challenges of real-world operations. In addition to recurrent training, every LAPD pilot completes FlightSafety’s dedicated Inadvertent Instrument Meteorological Conditions (IMC) course—preparing crews to safely respond when visibility is reduced by clouds, fog, heavy rain, snow, or darkness, requiring pilots to fly by instruments rather than by sight. 

“The only way to replicate something like inadvertent IMC is in a simulator, and not just any simulator,” said Gallagher. “It has to be a full-motion Level D flight simulator. There just isn’t a way to do it in the helicopter.” 

“Unexpectedly entering IMC can be one of the most dangerous situations a helicopter pilot can encounter. Losing visual reference can quickly lead to spatial disorientation, loss of control, or worse,” said FlightSafety Lead Flight Instructor Art Cawman, who trains LAPD pilots. “That’s why specialized, scenario-based training is vital. In my estimation, it is the single most deadly thing that can happen to a helicopter pilot because weather doesn’t care. It’s unpredictable, and our training teaches pilots how to recognize, avoid, and safely recover from these situations.”  

“We go from the beach to mountain terrain and there are certain things we can’t do in the helicopter,” added current LAPD Chief Pilot Chris Van Horn. “Realism is paramount when it comes to training. You want to be able to have very realistic training as frequently as possible. Simulator training should be done in every training program.” 

An Inside Look at FlightSafety International’s Cutting-Edge Mirror Displays

Inside a specialized facility in Broken Arrow, Oklahoma, flat sheets of glass are transformed into the large, ultra-precise, and realistic mirror displays found inside FlightSafety International’s (FSI) Full Flight Simulators (FFS). Qualified to the highest certification level of FAA 14 CFR Part 60 Level D, the displays known as CrewView, fill the entire aircraft window, playing a critical role in how the world’s top pilots train to be ready for anything.

FSI acquired CrewView from Glass Mountain Optics in 2009 and brought operations to Broken Arrow in 2022. A team of highly skilled specialists and technicians work at the plant, supported by FSI’s global engineering, manufacturing, and training teams. Many of the state-of-the-art processes in use today were developed and refined over decades by specialists like Bart Sloane, who has been in the industrial and simulation optics business for 40 years.  Sloane helped design the innovative ovens and polishing machines still in use today.

“I believe that our CrewView technology is made special because of the processes we have developed, refined, improved, adapted, and even abandoned over the last four decades,” said Sloane. “The result is that we have a reliable, predictable, repeatable, and flexible method for manufacturing some of the largest mirrors in the market using glass as the primary raw material.”

The proprietary manufacturing process of FSI’s advanced glass mirror displays begins with flat panels of glass passing through a series of highly specialized steps. After being heated and shaped into a perfect spherical shape, glass is cut, ground, and polished. Once pieces have passed a microscopic inspection, each piece is trimmed to its final shape with precision waterjet technology — allowing multiple panels to fit together so seamlessly that their joints virtually disappear in use. Glass pieces then receive multiple protective coating layers to provide maximum reflective uniformity across the entire surface of the mirror as well as excellent durability. The result is unmatched, clear, consistent, and realistic visuals.

In addition to large spherical glass mirrors for fixed-wing out-the-window displays, FSI also produces smaller curved mirrors for helicopter chin windows and is continually innovating to improve the CrewView line of displays, including developing light weight rigid mirrors.

In addition to engineering and manufacturing cutting-edge glass solutions, FSI has a second operation in Broken Arrow, which develops simulators and employs more than 640 people. Frasca, a FlightSafety International company that has been a global leader in flight simulation since 1958, operates an additional U.S. manufacturing plant in Urbana, Illinois, employing 145 people.