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FAA’s New Radio Altimeter Rules: What They Mean for Advanced Air Mobility and 5G

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There are more solutions than obstacles. Nicolas Zart

For those of you still wondering about the implications of the U.S.’s 5G deployment and its effect on aviation, the FAA’s new plan to replace or upgrade nearly all U.S. radio altimeters is a major safety and cost issue for airlines. Electric Air Mobility fears the cost will be further passed down to travelers. The plan will also affect how advanced air mobility (AAM) aircraft will integrate their operations safely into the national airspace as 5G expands. For AAM developers and operators, interference‑tolerant altimeters and solid spectrum policy are high on the list for certification, operations, and infrastructure planning.

US 5G networks differ greatly from those of Europe by emitting stronger frequencies, potentially disrupting flights. As the 5G network expands across the country, the FAA is moving to make radio altimeters more tolerant to interference. That decision will have long‑term effects on AAM, especially as it currently moves into the certification stage of its aircraft. The proposal requires aircraft to upgrade radio altimeters to upgrade or replace those systems so they can safely share spectrum with powerful wireless signals in the C‑band will mean extra costs endured by startups.

What the FAA is proposing

On 7 January 2026, the FAA published a proposed rule called “Requirements for Interference‑Tolerant Radio Altimeter Systems” in the Federal Register. The rule responds to the next phase of U.S. 5G deployment in the upper C‑band, between 3.98–4.2 GHz, which sits immediately below the 4.2–4.4 GHz band used by aircraft radio altimeters.

According to the industry, older altimeters were never designed to handle today’s combination of higher‑powered 5G signals, tower density, and proximity to airports and low‑level flight paths. When exposed to strong out‑of‑band emissions, some units can produce faulty height‑above‑ground readings, which in turn can affect automatic landing systems, terrain awareness and warning systems, and traffic‑collision avoidance.

Under the proposal, transport category airlines operating under Part 121 would face the earliest compliance dates, expected sometime between 2029 and 2032. There will be two additional years for other operators. The FAA estimates that thousands of altimeters will need to be replaced or upgraded, at a total industry cost in the billions of dollars.

The Effect on AAM and eVTOLs

AAM concepts rely heavily on precise, reliable altitude information at low level, especially during approach, landing, and operations near buildings and vertiports. Many eVTOL and eSTOL designs plan to fly frequent, short flights in dense urban environments, where 5G infrastructure is also concentrated. Those signal levels can be especially high.

Joby S4 eVTOL taking off - Picture Nicolas Zart
Joby S4 eVTOL taking off – Picture Nicolas Zart

To date, it is believed that interference-tolerant altimetry will not be optional for the expanding 5G network. And while AAM prototypes fly under experimental or special conditions today, future type-certificated aircraft will need more advanced avionics architectures that account for both current and future wireless deployments throughout their service life.

For AAM infrastructure, the evolving 5G environment will influence route design, obstacle‑clearance margins, and contingency procedures in low‑visibility or automation‑heavy operations. Ensuring that onboard sensors are resilient to nearby 5G transmitters will support higher dispatch reliability and reduce the need for operational restrictions around urban antennas and rooftop sites.

Lessons from the first 5G–altimeter clash

5G‑related radio altimeter concerns in aviation started in 2022 when U.S. wireless companies began activating lower C‑band services between 3.7–3.98 GHz in 2021–2022. The FAA issued airworthiness directives and domestic notices that limited some approaches and low‑visibility operations until altimeters could be tested or modified.

Those were temporary measures that disrupted some airline and business‑aviation schedules at airports with strong 5G signals. The new FAA guidance and performance standards aim to make aircraft compliant with altimeters that can be considered “5G C‑band tolerant,”. Today, most AAM startups have already completed the first wave of upgrades and now have to face the next upgrade.

The new proposal recognizes that the upper C‑band is even closer to the protected altimeter spectrum than the earlier deployments were and needs more robust performance margins. For AAM, this early regulatory attention offers a chance to build 5G resilience into designs before large fleets of eVTOL aircraft enter service in complex urban radio‑frequency environments.

FlyNow Aviation eCopters
FlyNow Aviation eCopters

AAM system design and certification implications

This could mean that AAM aircraft need extra layers of height‑sensing solutions combining radio altimeters with barometric altitude, GNSS, lidar, and vision‑based sensors. This will not only raise the complexity levels of the aircraft, but also add weight and raise their prices. It will also influence certification plans, safety assessments, and hazard analyses submitted to the FAA and other authorities, especially for operations in urban air mobility corridors. The FAA’s focus on interference‑tolerant altimeter safety means more redundancy in the industry.

This will greatly affect AAM concepts that depend on high levels of automation, including eventual autonomous operations. These aircraft will need certified sensor suites that can maintain safe performance even with evolving 5G and future 6G networks nearby. ​Ground infrastructure planners will have to coordinate more closely with telecommunications stakeholders when siting vertiports, landing pads, and low‑level routes. Understanding local tower locations, power levels, and frequency use will help operators design procedures that take advantage of interference‑tolerant altimeters while still maintaining buffer zones where needed.

Where to learn more

For readers following the advanced air mobility ecosystem, Electric Air Mobility’s news and education platform offers ongoing coverage of policy, technology, and infrastructure developments shaping AAM in the United States and abroad. Industry associations such as the National Business Aviation Association also provide practical guidance on 5G interference for business and emerging operators as they plan avionics upgrades.

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