Quick Answers
When must airlines replace radio altimeters under the FAA 5G rule?
Part 121 airlines and large Part 129 foreign carriers must install interference-tolerant radio altimeters by December 30, 2030. All other aircraft operating under Parts 91, 125, 133, 135, 136, 137, and 194 must comply by October 31, 2034. Approximately 58,500 altimeters across the US fleet must be replaced or modified.
How much does the FAA radio altimeter upgrade cost per aircraft?
The FAA estimates the radio altimeter replacement or modification costs $80,000 to $120,000 per aircraft. Total US fleet compliance cost is approximately $4.49 billion. The FAA estimates total benefits exceed $8 billion, primarily from removing the operational restrictions imposed by current 5G airworthiness directives.
Quick Compliance Summary
| Regulatory body | Federal Aviation Administration (FAA) |
| Instrument | Final rule: Requirements for Interference-Tolerant Radio Altimeter Systems |
| Issued | July 24, 2026 |
| What it requires | All radio altimeters operating in US airspace must meet next-generation interference-tolerance performance requirements |
| Units affected | Approximately 58,500 radio altimeters across the US civilian fleet |
| Tier 1 deadline | December 30, 2030 — Part 121 airlines and large Part 129 foreign carriers (30+ seats or >7,500 lb payload) |
| Tier 2 deadline | October 31, 2034 — all other aircraft with radio altimeters |
| Estimated cost | $80,000–$120,000 per aircraft; $4.49 billion total US fleet |
| Estimated benefit | Over $8 billion — from removal of operational restrictions |
| Coordinated with | FCC Report and Order clearing 160 MHz of Upper C-band (3.98–4.14 GHz) for 5G auction |
Who Should Read This
This update is directly relevant to:
- Directors of Maintenance and Fleet Planning at Part 121 airlines
- Continuing Airworthiness Managers (CAMs) across all operation types
- Part 135 charter and air ambulance operators
- Part 91 corporate and GA operators
- MRO Planning Teams scheduling avionics upgrades
- Avionics procurement and budgeting departments
- Foreign carriers (Part 129) operating into the United States
- Radio altimeter and avionics manufacturers
Every aircraft with a radio altimeter operating in US airspace will eventually be affected by this rule. The question is not whether your fleet needs to comply — it is when.
At a Glance
| Item | Details |
|---|---|
| Rule type | Final rule — new Part 87 performance requirements |
| Issued | July 24, 2026 |
| NPRM published | January 7, 2026 |
| Legislative mandate | One Big Beautiful Bill Act, Section 40002 (July 2025) |
| FCC coordination | Report and Order adopted July 22, 2026 — 160 MHz Upper C-band (3.98–4.14 GHz) cleared for auction |
| 5G auction timeline | FCC auction to close by mid-2027 |
| New 5G services operational | December 2030 (75 largest US markets); July 2031 (nationwide) |
| Tier 1 compliance | December 30, 2030 — Part 121 + large Part 129 (30+ seats / >7,500 lb payload) |
| Tier 2 compliance | October 31, 2034 — all other aircraft (Parts 91, 125, 133, 135, 136, 137, 194, remaining Part 129) |
| Units to replace/modify | ~58,500 radio altimeters |
| Cost per aircraft | $80,000–$120,000 |
| Total US fleet cost | ~$4.49 billion |
| Total estimated benefit | Over $8 billion |
| Performance standard | RTCA/EUROCAE MOPS — joint standard planned for publication by March 2027 |
What This Rule Does
This final rule establishes new minimum performance requirements for radio altimeter systems operating in US airspace. Every radio altimeter must be capable of providing accurate altitude readings in the presence of 5G wireless interference from neighboring spectrum bands.
The rule does not impose new operational restrictions. It does the opposite. It creates the permanent equipment standard that will eventually make the interim AFM limitations — imposed through eight type-specific Canadian airspace ADs and the earlier US domestic 5G AD — unnecessary.
Once an aircraft’s radio altimeters meet the new standard, that aircraft is interference-tolerant. Interference-tolerant aircraft do not need AFM limitations for 5G environments. The temporary restrictions go away.
Why This Rule Exists Now
This final rule is the product of a coordinated federal action spanning two agencies and one Act of Congress.
July 2025: President Trump signed the One Big Beautiful Bill Act. Section 40002 directed the FCC to conduct competitive bidding for at least 100 MHz in the Upper C-band (3.98–4.2 GHz).
January 7, 2026: The FAA published an NPRM proposing the radio altimeter upgrade requirements.
July 22, 2026: The FCC adopted its Report and Order making 160 MHz of Upper C-band available for 5G terrestrial wireless use through a competitive auction. The FCC will close the auction by mid-2027.
July 24, 2026: The FAA issued this final rule, coordinated with the FCC action. The rule ensures the aviation fleet is equipped with interference-tolerant altimeters before new 5G services begin operating in the Upper C-band.
New 5G wireless services are authorized from December 2030 in the 75 largest US markets and from July 2031 nationwide. The Tier 1 aviation compliance deadline (December 30, 2030) is set to ensure commercial airline fleets are ready before the first Upper C-band services go live.
Why It Matters — The Full 5G Story in Context
This rule is the capstone of a regulatory story that began in 2020.
In 2020, RTCA formed a special committee to study whether 5G emissions in the 3.7–3.98 GHz Lower C-band could interfere with radio altimeters operating in the 4.2–4.4 GHz band. The answer was yes — under certain conditions.
From 2021 onward, the FAA, FCC, airlines, and telecommunications industry clashed over the Lower C-band rollout. The FAA issued AD 2023-10-02 for US domestic airspace. In 2026, Canada removed its own Lower C-band mitigations, triggering eight type-specific Canadian airspace ADs — all covered in the ARW 5G series.
Those ADs were interim solutions. They imposed operational limitations because existing radio altimeters could not tolerate interference. The limitations were a safety patch, not a fix.
This final rule is the fix. It mandates an equipment upgrade that eliminates the vulnerability to interference at its source. Once the fleet is equipped, the AFM limitations become unnecessary.
The FCC’s parallel action — clearing the Upper C-band for auction — adds urgency. The Upper C-band (3.98–4.14 GHz) sits even closer to the altimeter band (4.2–4.4 GHz) than the Lower C-band (3.7–3.98 GHz). Without interference-tolerant altimeters, Upper C-band 5G services would create an even more severe interference environment than the one that triggered the 2023 and 2026 ADs.
FCC safeguards help but do not eliminate the need for the equipment upgrade. The FCC’s Report and Order includes power limits on auctioned 5G signals, a buffer band between the 5G and altimeter frequency ranges, tower height limits, and protections for TAWS alerting systems. These reduce the interference risk. The FAA’s altimeter rule ensures the aviation fleet can operate safely even if those mitigations prove insufficient over time.
The Two-Tier Compliance Structure
The FAA set two deadlines to align with the 5G rollout schedule and operational priorities.
Tier 1 — December 30, 2030
Applies to: Part 121 scheduled air carriers and Part 129 foreign air carriers operating aircraft with 30 or more passenger seats or a payload capacity exceeding 7,500 pounds.
These operators must install interference-tolerant radio altimeters by December 30, 2030. This is before the FCC authorizes Upper C-band services in the largest markets (December 2030).
The rationale: scheduled airlines operating high-frequency commercial operations in low-visibility conditions have the greatest exposure to altimeter-dependent safety systems. They must be equipped first.
Tier 2 — October 31, 2034
Applies to: All other aircraft with radio altimeters that must comply with Part 91, including aircraft operating under Parts 125, 133, 135, 136, 137, 194, and remaining Part 129 aircraft not in Tier 1.
These operators have until October 31, 2034. This covers Part 135 charter operators, corporate aviation, air ambulance, agricultural operations, and GA aircraft with radio altimeters.
Cost and Benefit
The FAA estimates the following:
| Item | Amount |
|---|---|
| Units to replace/modify | ~58,500 radio altimeters |
| Cost per aircraft | $80,000–$120,000 |
| Total US fleet compliance cost | ~$4.49 billion |
| Total estimated benefit | Over $8 billion |
| Net benefit | Positive — benefits exceed costs |
The $8 billion benefit comes primarily from the removal of operational restrictions. The interim AFM limitations imposed by the 5G ADs restrict operations, increase crew workload, complicate dispatch procedures, and, in some cases, prevent low-visibility approaches entirely. Eliminating those restrictions restores full operational capability.
What Operators Should Do Now
Tier 1 operators (Part 121 and large Part 129):
The December 30, 2030 deadline is four years and five months away. That sounds distant, but 58,500 altimeters across the US fleet cannot all be replaced in the final year. Supply chain, MRO capacity, and aircraft scheduling all require multi-year planning.
- Begin fleet-wide radio altimeter inventory now. Identify which units are installed, their current part numbers, and whether they already meet the new standard or can be modified to do so.
- Engage your avionics suppliers. Confirm lead times for next-generation altimeter units or modification kits.
- Build the upgrade into your fleet maintenance planning cycle. A four-year window means incorporating the replacement into scheduled heavy maintenance checks — C-checks or equivalent — rather than scheduling standalone avionics inputs.
- Monitor the RTCA/EUROCAE MOPS standard. The joint industry standard defining the specific performance requirements is planned for publication by March 2027. Your procurement specifications should align with this standard.
Tier 2 operators (Part 135, Part 91, GA):
The October 31, 2034 deadline gives more time. But the same supply chain will serve both tiers. Start planning now to avoid competing with Tier 1 operators for altimeter units and MRO slots in 2029–2030.
Connection to the ARW 5G AD Series
This rule closes the regulatory loop that began with the first 5G AD in 2023. The eight type-specific Canadian airspace ADs published on ARW — covering the 737 MAX, 737 Classic/NG, 787, 747-8/777, 747 Classic/400, 757/767, and legacy Boeing/MD fleet — were all interim measures addressing a fleet that was not yet equipped to tolerate 5G interference.
This final rule mandates the equipment that makes those interim measures unnecessary. Once an aircraft’s altimeters meet the new standard, the AFM limitations imposed by the 5G ADs no longer apply.
The transition will not be instantaneous. The 5G ADs remain in force until each individual aircraft is equipped. But the end state is now defined: an interference-tolerant fleet operating without operational restrictions in a fully deployed 5G environment.
Key Dates
| Event | Date |
|---|---|
| RTCA 5G interference study began | April 2020 |
| FAA AD 2023-10-02 (US domestic 5G) | 2023 |
| One Big Beautiful Bill Act signed (Section 40002) | July 2025 |
| NPRM published | January 7, 2026 |
| Canadian 5G mitigations removed / 8 type-specific ADs published | July 1, 2026 |
| FCC Report and Order adopted (Upper C-band auction) | July 22, 2026 |
| FAA final rule issued | July 24, 2026 |
| RTCA/EUROCAE MOPS standard planned publication | March 2027 |
| FCC Upper C-band auction closes | Mid-2027 |
| Tier 1 compliance (Part 121 + large Part 129) | December 30, 2030 |
| New 5G services in 75 largest US markets | December 2030 |
| New 5G services nationwide | July 2031 |
| Tier 2 compliance (all other aircraft) | October 31, 2034 |
Source Documents
- FAA — Statement on 5G (July 22, 2026)
- FAA — Requirements for Interference-Tolerant Radio Altimeter Systems (final rule)
- Federal Register — NPRM: Requirements for Interference-Tolerant Radio Altimeter Systems (January 7, 2026)
- FCC — Report and Order, Upper C-band spectrum auction (July 22, 2026)
- Related ARW articles: 5G Canadian Airspace AD series (Articles 10, 12, 14, 21, 22, 25, 27)
FAA radio altimeter final rule 5G interference: FAQ
Does this rule replace the existing 5G airworthiness directives?
Not immediately. The existing ADs remain in force until each individual aircraft is equipped with interference-tolerant altimeters. Once an aircraft’s altimeters meet the new standard, the AFM limitations imposed by the 5G ADs no longer apply to that aircraft.
How many radio altimeters need to be replaced?
The FAA estimates that there are approximately 58,500 radio altimeters across the US civilian fleet.
What is the cost per aircraft?
The FAA estimates $80,000 to $120,000 per aircraft for the altimeter replacement or modification.
When must Part 121 airlines comply?
By December 30, 2030. This is before the FCC authorizes new 5G services in the Upper C-band in the largest US markets.
When must Part 135 and Part 91 operators comply?
By October 31, 2034.
What is the Upper C-band and why does it matter?
The Upper C-band (3.98–4.14 GHz) is the spectrum the FCC cleared for new 5G auction. It sits closer to the altimeter band (4.2–4.4 GHz) than to the Lower C-band (3.7–3.98 GHz), which triggered the original 5G interference concerns. Without interference-tolerant altimeters, Upper C-band 5G services would create a more severe interference environment.
What is the RTCA/EUROCAE MOPS standard?
A joint US-European industry standard defining the minimum operational performance specification for interference-tolerant radio altimeters. It is being developed by RTCA SC-239 and EUROCAE WG-119. Publication is planned by March 2027. Operators should align procurement specifications with this standard.
Is there a performance standard I can procure against today?
Not yet in final form. The RTCA/EUROCAE MOPS is in draft validation. The FAA has requested publication by mid-2026 if possible, but March 2027 is the planned date. Engage your avionics suppliers now to understand their product development timeline against this standard.
Related Reading:
- FAA AD 2026-13-16: Boeing 757 and 767 Family — 5G Canadian Airspace Requires Two-Part AFM Revision
- FAA AD 2026-13-14: Boeing 747 Classic and 400 Series — 5G Canadian Airspace Limitations: Complete the Type-Specific AD Series
- FAA AD 2026-13-15: 5G Canadian Airspace Limitations Now Cover Boeing 707, 717, 727, DC-8, DC-9, DC-10, MD-11, and MD-80/90 Series
- FAA AD 2026-13-11: Boeing 787 Dreamliner 5G Canadian Airspace Limitations — Effective July 1, 2026
- FAA Issues Emergency Radio Altimeter ADs for Canadian Airspace — Effective July 1, 2026
aviationregwatch.com publishes regulatory intelligence for aviation compliance professionals. This article is an informational summary, not legal or airworthiness advice. Consult your avionics manufacturer, CAMO, or legal counsel for compliance decisions.