5G Interference in Aviation-An Emerging Issue

The global rollout of fifth generation (5G) cellular networks has placed the aviation industry in a direct collision course with telecommunications regulators over a strip of radio frequency spectrum that sits immediately adjacent to the band used by aircraft radio altimeters. According to a report published in AeroTime, the Federal Aviation Administration (FAA) confirmed, as of August 2025, that it had received 659 reports of potential C-band interference, including 493 associated with radio altimeters or related systems — and had identified 118 events in which C-band interference was treated as a probable contributing factor after eliminating other causes.

Radio altimeters are the instruments that tell pilots and automated systems precisely how far an aircraft is above the ground during approach and landing — information that is critical under low-visibility conditions. Radio altimeter anomalies that go undetected, particularly close to the ground during landing flare, could lead to loss of continued safe flight and landing, according to FAA Airworthiness Directive 2023-10-02.

The issue has now crystallized into a financial and regulatory confrontation of considerable scale. In a Notice of Proposed Rulemaking (NPRM) issued on January 7, 2026, the FAA proposed requiring US aircraft operators to replace or upgrade roughly 58,600 radio altimeters at an estimated total cost of $4.5 billion, triggered by the Trump administration’s decision to auction additional Upper C-band spectrum to wireless carriers under the One Big Beautiful Bill Act.

The proposal marks the second major cycle of altimeter disruption the industry has faced since 2022 — and this time, the financial burden is substantially larger. Meanwhile, beyond the United States, voluntary mitigation agreements in Canada and Australia were set to expire in January and April 2026 respectively, and next-generation altimeters immune to the threat are not expected to be commercially available to airlines before the early 2030s.

How do 5G Signals Threaten Radio Altimeters?

A radio altimeter — also called a radar altimeter — operates by transmitting a signal downward from the aircraft and measuring the time it takes for that signal to reflect back from the ground. Radio altimeters operate in the 4.2–4.4 GHz frequency band, providing accurate altitude readings above ground level. These readings are a critical input for:

• landing systems
• terrain awareness systems
• autopilot functions.

When any of these inputs fail or provide erroneous data, the consequences cascade: the autothrottle, the Ground Proximity Warning System (GPWS), thrust reversers, and the Traffic Collision Avoidance System (TCAS) can all malfunction or provide incorrect outputs.

5G C-band networks in the United States operate between 3.7 and 3.98 GHz. The top end of the C-band 5G allocation — 3.98 GHz — leaves a 220 MHz buffer with the lower edge of the radio altimeter band at 4.2 GHz. That gap may sound sufficient, but it is not absolute protection.

Legacy radio altimeters, designed decades before 5G existed, were built with limited out-of-band filtering. Their receivers were not engineered to reject powerful adjacent signals of the strength now produced by terrestrial 5G base stations, which in the United States operate at power levels higher than any other 5G deployment currently in use elsewhere in the world. When a ground station emits a strong 5G signal, the older altimeter’s receive circuitry can be desensitized or overwhelmed, producing erroneous altitude readings — or no reading at all.

Interference can manifest in two ways. The first is direct in-band intrusion, where 5G spurious emissions leak into the 4.2–4.4 GHz altimeter band. The second, more common form, is what engineers call receiver desensitization: the altimeter’s circuits are overwhelmed by the intensity of an adjacent signal, degrading their ability to process the genuine return echo.

The Air Line Pilots Association (ALPA) notes that radar altimeter interference can take the form of loss of radar altitude information, or worse, incorrect radar altitude information. This means that the system does not fail safely to zero but instead may display a plausible but false altitude reading that neither the automation nor the pilot may detect in time.

Beyond radio altimeters, the broader category of spectrum risk to aviation encompasses GPS and Global Navigation Satellite System (GNSS) interference. IATA Director General Willie Walsh stated at an industry event in Geneva that GPS spoofing and jamming incidents are increasing rapidly across the world, describing the problem as not merely a technical concern but an operational vigilance issue for pilots.

US Aircraft Operators Might Need 58,600 Radio Altimeters.

The aviation industry’s warnings about 5G spectrum risks were not last-minute. Airlines for America filed formal comments with the Federal Communications Commission (FCC) in May 2018, raising concerns about potential interference with aircraft radio altimeters from the planned use of adjacent C-band frequencies. The FCC nonetheless proceeded, and in early 2021 awarded C-band spectrum between 3.7 and 3.98 GHz to US wireless carriers, with AT&T and Verizon spending over $81 billion in the auction.

The following timeline maps the escalation:

• November 2021: The FAA issued Safety Alert for Operators SAFO 21007, warning of potential adverse effects of 5G C-band transmissions on radio altimeters, and issued Special Airworthiness Information Bulletin SAIB AIR-21-18 requesting data from manufacturers and operators.
• January 2022: AT&T and Verizon activated their 5G C-band networks on January 19, 2022, but agreed to maintain buffer zones around airports and reduce transmission power at 188 airports under a voluntary agreement with the FAA. As of February 4, 2022, the FAA had issued NOTAMs identifying 1,931 locations around the US where 5G interference was present.
• July 2023: The FAA issued an altimeter retrofit deadline, requiring airlines to upgrade airplane altimeters by July 1, 2023, to ensure they would not face interference. The deadline came into effect just before new rules prohibiting certain landings in low-visibility conditions without upgraded altimeters. The risk of 5G interference to commercial passenger aircraft was considered successfully mitigated by the end of September 2023 — temporarily.
• January 2026: The FAA issued a new NPRM requiring replacement or upgrade of approximately 58,600 radio altimeters across the US civil aviation fleet at a cost of at least $4.5 billion. This second mandate was triggered by the government’s plan to auction the Upper C-band (3.98–4.2 GHz) — a band that sits directly adjacent to the altimeter allocation, leaving essentially no guard band.

The NPRM’s compliance window spans 2029 to 2039 for larger commercial aircraft, depending on equipment availability and retrofit feasibility. Smaller general aviation aircraft would be required to comply within two years of the final rule’s publication.

Who Will Pay the $4.5 Billion for Altimeters?

The financial exposure created by the FAA’s January 2026 NPRM is substantial, and the question of cost allocation remains contested. The FAA estimates the total cost of retrofitting interference-tolerant altimeters across the US fleet at $4.49 billion, or $424 million annualized at a 7% discount rate over 20 years. This figure covers roughly 58,600 units across commercial air carriers operating under FAR Parts 121 and 129, and aircraft with 30 or more passenger seats or payloads exceeding 7,500 pounds.

The wireless industry’s position is that this cost should rest entirely with aviation operators. The aviation industry’s position, backed by the FAA, is that the interference risk is created by spectrum expansion authorized by the government, and that government support for the retrofit program is therefore appropriate. The FCC’s November 2025 proposed rule on Upper C-band noted the altimeter problem and invited comment on specific proposals and mechanisms to facilitate retrofits from a financial perspective — leaving open the possibility of payments to airlines, operators, and manufacturers.

The broader economic pressure is well-articulated by the telecom industry’s own lobbyists. Consulting firm Accenture stated in a 2025 report that US wireless networks face a looming capacity crisis, with dire implications for the broader economy if new spectrum cannot be made available for 5G.

That argument frames the aviation retrofit cost as the price of maintaining US competitiveness in data-intensive sectors including artificial intelligence. The aviation industry has not accepted this framing.

How Different Countries Handle 5G Aviation Mitigation

The United States’ approach to 5G near airports represents one end of the policy spectrum — high-power deployment with voluntary, time-limited mitigation. Much of the rest of the world has adopted more conservative postures.

IATA has noted that countries still working on 5G deployment plans can gain significant insights from states that have already experienced the challenges of safely dealing with radio interference issues affecting aviation. The implicit lesson is that the US model — high power, close proximity, voluntary mitigation with a time limit — has generated costs and risks that a more cautious initial deployment would have avoided.

IATA, ICAO, And the Push for a Global Framework

The regulatory response to 5G interference has been fragmented by national jurisdiction, and the aviation industry has increasingly pushed for a binding global framework to replace the patchwork of voluntary agreements and bilateral negotiations.

In November 2025, IATA submitted a working paper to the International Telecommunication Union’s (ITU) Working Party 5B meeting in Geneva, outlining the operational scenarios and safety requirements that should govern 5G and 6G deployment near aviation frequencies. The submission was timed ahead of the World Radiocommunication Conference 2027 (WRC-27), at which the ITU will set the long-term framework for global 5G and 6G spectrum policy. IATA urged the ITU and national telecommunications regulators to ensure that 5G and future 6G networks operating near aviation frequencies do not impair radio altimeters and other avionic systems.

IATA’s submission carried an explicit warning: next-generation radio altimeters more resistant to 5G interference are not expected to be commercially available to airlines before the early 2030s. This creates a multi-year window during which aviation is exposed to increasing interference risk without a hardware solution. IATA stated that “the industry needs clear, consistent safeguards to bridge the period before new altimeters are available”.

In June 2025, EASA and IATA jointly published a comprehensive mitigation plan addressing GNSS interference more broadly, concluding that a broader and more coordinated approach was needed across four areas: improved information gathering, stronger prevention and mitigation measures, more effective use of infrastructure and airspace management, and enhanced coordination among relevant agencies. The plan acknowledged that GNSS interference events, driven partly by military jamming in conflict zones, have spread well beyond the Middle East and Eastern Europe into Asia and other regions.

The aviation industry’s GNSS interference exposure is a compounding threat. Aviation authorities have warned that GPS interference has spread across a widening range of high-risk airspace, stretching from the eastern Mediterranean and Black Sea to the Russia-Baltic region, the India-Pakistan border, Iraq and Iran, and the Korean Peninsula.

India’s Civil Aviation Ministry confirmed to Parliament that between November 2023 and November 2025, a total of 1,951 GNSS interference cases were reported by Indian carriers, following the Directorate General of Civil Aviation (DGCA)’s November 2023 advisory circular mandating such reports.

Next-Generation Altimeters and the Honeywell ALA-52B

The engineering response to the interference problem has two distinct tracks: the near-term retrofit of existing altimeters with improved filtering, and the longer-term development of fully 5G-tolerant next-generation units.

In the near-term category, the most significant development has been the Honeywell ALA-52B. Electromagnetic interference testing performed by Honeywell on behalf of the FAA demonstrated that the ALA-52B is the only certified radio altimeter currently available on Airbus and Boeing aircraft that can withstand 5G interference.

The ALA-52B achieves 5G tolerance through enhanced bandpass filtering that prevents C-band energy from leaking into the altimeter’s receiver circuits. Manufacturers including Honeywell, Collins Aerospace, and Thales have led retrofit programs across commercial and business aviation fleets, prioritizing aircraft types most exposed to low-altitude 5G signal environments.

The longer-term hardware solution faces a different constraint: next-generation radio altimeters that are more resistant to 5G are not expected to be available to airlines before the early 2030s. The RTCA — the US-based aviation standards body — plans to publish new minimum operational performance standards (MOPS) for interference-tolerant altimeters in March 2027, though the FAA has urged that deadline be moved to June 2026. Meeting the revised deadline would align with the FAA’s planned publication of its final rule on altimeter standards, which it says will conform to those standards.

Beyond hardware, US aerospace and wireless groups are also working on a software and network solution: virtual exclusion cylinders around 5G antennas, which would create geofenced zones of reduced power output in the immediate vicinity of airports. This approach would reduce the physical retrofit burden but requires wireless carriers to accept operational constraints on their network infrastructure near airports — a trade-off that the telecom industry has historically resisted.

GNSS Spoofing and the Compound Navigation Threat

The 5G altimeter story comes alongside a rapidly growing threat from GPS jamming and spoofing that, while distinct in its origins, compounds the navigation vulnerability that aviation faces.

ICAO has formally condemned GNSS interference by Russia and North Korea, reaffirming the principle that interference with civil aviation navigation systems constitutes a violation of international obligations. Russia acknowledged jamming operations affecting civil receivers in the Baltic Sea region in June 2025 and indicated those operations would continue for military reasons. The Middle East, Eastern Europe, and increasingly South and Southeast Asia have all seen documented interference events.

With spoofing, a false GNSS signal is transmitted, causing airborne receivers to produce false position outputs, sometimes without triggering cockpit warning annunciations. This is particularly dangerous because pilots may not realize their position data is corrupted until a secondary cross-check reveals the discrepancy. Airlines and operators have adopted a range of countermeasures such as:

• rerouting flights around high-risk airspace
• enhanced crew training on GNSS-degraded procedures
• multi-frequency GNSS receivers
• controlled reception pattern antennas
• greater reliance on inertial navigation systems as backup references