FAA proposes radar altimeter replacements that could cost US aviation $4.5B

The Federal Aviation Administration has proposed new rules that would require US aircraft operators to replace or upgrade roughly 58,600 radio altimeters, at an estimated cost of about $4.5 billion, as the federal government moves to open additional 5G spectrum for wireless carriers.  In a Notice of Proposed Rulemaking issued on January 7, 2026, the FAA said it wants all radio altimeter systems installed on aircraft operating in the airspace of the 48 contiguous US states and the District of Columbia to meet new minimum interference-tolerance standards. The proposal aims to ensure altimeters continue to provide accurate height-above-terrain data as wireless carriers expand services in the Upper C-band, a slice of 5G wireless spectrum immediately adjacent to the band used by radio altimeters.    The proposal results from the One Big Beautiful Bill, signed in July 2025, which reinstated the Federal Communications Commission’s general auction authority and directed the agency to complete competitive bidding for not less than 100 MHz in the Upper C-band.     The FAA said it intends the new requirements to preserve “safe, efficient, and reliable” aviation operations as wireless carriers expand services in spectrum adjacent to the band used by radio altimeters.  

Safety concerns

Radio altimeters, also called radar altimeters, measure an aircraft’s height above terrain and obstacles using low-power signals in the 4.2-4.4 GHz band. Pilots use that information directly, and many aircraft systems depend on it to function properly. The FAA cited a wide range of uses, including low-visibility approach and landing functions such as autoland and enhanced-vision operations, as well as for safety systems like terrain awareness and warning, wind shear alerts, and traffic collision avoidance.  

The core concern, the FAA said, is that higher-powered terrestrial wireless signals in neighboring bands can interfere with an altimeter’s ability to detect faint reflections from the ground. That can lead to erroneous altitude readings, missing readings, or nuisance alerts in systems that rely on accurate height-above-ground data. At very low altitude, the FAA said, those failures can create hazardous conditions that a pilot may not detect in time to correct.  

The proposal lays out a staggered compliance schedule. The FAA would require aircraft operating under Part 121, along with large Part 129 aircraft with 30 or more passenger seats or a payload capacity above 7,500 pounds, to meet the new minimum performance standards by the date the FCC authorizes wireless services in the Upper C-band. For all other aircraft equipped with radio altimeters, the FAA would require compliance two years later.  

The FAA said it expects the initial compliance deadline will be achievable sometime between 2029 and 2032, depending on factors such as equipment availability and retrofit capacity. The agency said it will set the final deadlines in the final rule after reviewing public comments.  

Long-term solution

The NPRM also tries to put the proposal in the context of the long-running Lower C-band dispute. Wireless services already operate in the 3.7-3.98 GHz range, which sits below the Upper C-band. The FAA noted that it issued airworthiness directives in 2021 and later years to address unsafe conditions tied to potential interference, and it pointed to voluntary steps taken by wireless providers to reduce disruption.  

Those voluntary commitments, the FAA said, will come to an end on January 1, 2028, unless the parties extend or modify them. The FAA argued that the current approach does not provide a long-term solution for either existing Lower C-band operations or future Upper C-band expansion.  

The agency also included data it says supports the interference risk. The FAA said it began tracking reports of potential interference in January 2022. As of August 19, 2025, it had received 659 reports of potential C-band interference, including 493 associated with radio altimeters or related systems. After analyzing 625 reports, the FAA said it identified 118 events in which it eliminated other likely causes and treated C-band interference as a potential factor. The FAA said most of those events involved radio altimeter display errors and nuisance alerts from systems that depend on radio altimeter inputs. The post FAA proposes radar altimeter replacements that could cost US aviation $4.5B appeared first on AeroTime.

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