An article by Giancarlo Buono, Group Director Safety and Airspace Regulation, United Kingdom Civil Aviation Authority
Incidences of global navigation satellite systems (GNSS) radio frequency interference (RFI) have increased dramatically over the past few years. National aviation authorities (NAAs) all over the world are working collaboratively to understand the complex interactions of GNSS RFI events with aircraft systems, mitigate the impact, and effectively manage the effects on the air traffic management (ATM) environment. The work requires skills and expertise from across the industry and aims to ensure that the modernisation of ATM is not disrupted.
Satellite navigation in the modern world
GNSS services such as the Global Positioning System (GPS) or Galileo play a pivotal role in supporting the aerospace industry and bring significant operational and safety benefits. This system, also known as satellite navigation, supports our everyday lives in a range of ways, be it location data used by emergency services and logistics tracking, or timing signals used for key infrastructure such as mobile phone networks, broadcast transmitters, and finance systems. Even ordering a takeaway meal depends on GNSS, which illustrates how integral the system is in our modern lives.
Aviation is no different, and uses GNSS to provide positional and timing data for a range of applications, including navigation, aircraft tracking, and terrain avoidance.
Modern systems such as uncrewed aerial vehicles (UAVs), and future technologies such as electric vertical take-off and landing (eVTOL) are expected to place additional dependencies on GNSS as their prevalence in the aviation system grows.
Growing trends in radio frequency interference
As we become increasingly dependent on GNSS for a wider array of capabilities and functions, it becomes a bigger target for disruption. Various forms of military equipment, both crewed and uncrewed, rely on GNSS for navigation and targeting. Militaries and non-State actors therefore have an interest in interfering with signals used by their adversaries. Recent years have seen a dramatic increase in GNSS RFI associated with conflict zones globally, and civil aircraft often suffer from the collateral impact of the interference, which can extend far beyond conflict zones themselves.
The effects of a GNSS interference event may not be limited to the area where the signal is disrupted. In some cases, the effects can be sustained over long distances, with aircrews having to follow set procedures to try to restore functions during the flight, which is not always possible. This can lead to a potential need for increased separation, reducing airspace capacity.
Assessing the impact
By design, aviation is not as dependent on GNSS as some other industries, and the safety-critical nature of our industry means we already have effective alternative means for ensuring safe operations. Aircraft operated for many years before the first GNSS receiver was certified in 1994. In the intervening 30+ years, more systems have been introduced that use GNSS, but the fundamental multilayered approach to safety means that aircraft can safely operate in a GNSS-denied environment.
One of the alternative means of navigation is the terrestrial system of Distance Measuring Equipment (DME) beacons that the UK and other States have maintained for many years. The UK currently has over 50 beacons that provide a GNSS-independent means of navigation. Whilst the accuracy may be limited when compared with modern satellite systems, DME and other terrestrial navigation aids continue to provide an alternative position source for aircraft. This system works alongside aircraft systems, including onboard inertial navigation capabilities, to provide a suite of positioning sources.
Enhancements to GNSS such as space-based augmentation system (SBAS) have enabled capabilities such as performance-based navigation (PBN), which introduces the ability to reduce separation distances and enable operations in and out of airports without terrestrial navigation systems. This results in greater capacity and the ability to operate in a wider range of weather conditions.
Mitigating the impact
To mitigate the effects of GNSS jamming and spoofing, a multifaceted approach is required. Discussions have focused on the development of more resilient avionics standards and architectures, potential authentication of GNSS signals, and controls around the procurement, possession, and use of illegal jammers. These longer-term measures should be explored alongside short- to medium-term work to investigate flight crew management, protection of terrestrial-alternative navigation aids and the reporting of interference events by pilots, airspace users and air navigation service providers (ANSPs).
Building greater resilience
In the flight deck, much work has been completed to better understand the implications for a broad range of avionics, and work is ongoing to make aircraft avionics architectures more resilient against the effects of GNSS interference. This is likely to include the use of military technologies, such as controlled reception pattern antennas and more robust receivers. To bolster existing systems, aircraft manufacturers have distributed guidance to operators regarding detection and mitigation techniques in the flight deck. The capability to detect such occurrences is dependent on the aircraft and equipment onboard.
Equally, improvements to GNSS signals, such as authentication services like Galileo Open Service Navigation Message Authentication (OSNMA), can provide assurance that the received messages have not been tampered with or modified.
Optimising infrastructure for a new age
As part of its work to modernise its airspace, the UK is working with NATS (En-Route) to develop plans to optimise Communications, Navigation and Surveillance (CNS) infrastructure. This work is in line with International Civil Aviation Organization (ICAO) recommendations to ensure considerations are made to the availability of terrestrial navigation and surveillance systems across the globe.
The UK is also supporting work within ICAO to develop new Standards and Recommended Practices for new satellite navigation and augmentation technologies. This includes the advent of dual-frequency multi-constellation GNSS receivers and new aircraft-based signal augmentation technologies.
GNSS interference is not just an aviation problem, and the UK government, like many States, is exploring cross-government dependencies on GNSS and establishing options to provide greater resilience. A loss of GNSS services is recognised in the UK’s National Risk Register as a significant risk due to the increasing reliance on GNSS from critical sectors, including transport. The UK Civil Aviation Authority (CAA) is also working closely with relevant government departments, agencies, and regulators to consider the issue of illegitimate use of radio frequency jamming devices.
Ensuring pilots have the information they need
The operational effects of GNSS RFI events on aircraft systems are now well understood. However, the CAA continues to work with UK operators through a number of forums to ensure they are effectively managing the risk of interference. This includes regular opportunities to gather information on the effects of interference events and ensure this is adequately shared with other operators. Information for pilots is actively updated to ensure that aircrews are aware of known international interference hotspots, which alongside generic information, is cascaded through a national safety notice (SN-2025/006).
NATS has implemented several defensive controlling measures, and its policy and procedures have evolved to better equip operational teams in handling aircraft impacted by GNSS spoofing incidents. Regular briefings are now provided to air traffic controller (ATC) operational teams to enhance response capabilities.
Reporting of interference, and planning for the worst
Collection and analysis of occurrence data remains critically important. Currently, it is highly dependent on aircrew reporting, which can be analysed by regulatory authorities to establish trends that could ultimately be investigated by radio regulatory authorities. Whilst this information is highly valuable, the automation of interference detection could provide a step change to how GNSS is monitored. Some States are exploring the use of surveillance technologies to identify the proliferation of interference events automatically. In the future, it is hoped that this approach will provide live data which can be rapidly communicated to the cockpit.
The UK government is working with NATS and the CAA to raise awareness of GNSS interference risks and strengthen coordination through clearly defined escalation pathways and mitigations for worst-case scenarios within UK airspace. While most current incidents involve aircraft affected by spoofing abroad, the threat of UK-based jamming or spoofing is increasing due to the growing accessibility of interference devices and software.
To better understand interdependencies within international airspace, the UK government, CAA, and NATS took part in the EUROCONTROL Aviation Crisis Coordination Cell (EACCC) exercise simulating a large-scale GNSS interference event. Building on this, a domestic airspace exercise was conducted in April 2025 to test escalation procedures and refine risk categorisation of interference events. As GNSS-related threats continue to evolve and airline mitigation strategies develop, regular scenario-based exercises remain critical to strengthening aviation response and resilience.
The increase in GNSS interference events has caused a number of challenges for operators, aircrews, regulators and ANSPs. A coordinated approach to short-, medium- and long-term mitigations will help to alleviate the impact of jamming/spoofing events, and provide greater resilience so that the reach of jamming equipment is minimised. The CAA and wider UK government are involved in multiple workstreams to effectively manage the risk and help to provide a sustainable position, navigation and timing capability for the aviation industry. This includes international engagement with ICAO and EUROCONTROL to ensure a globally coordinated approach to this growing issue.
This article was originally published in the summer 2025 edition of ECAC NEWS #83 .