Regulatory Alert: FAA Releases Final Rule on Aircraft Altimeter Retrofit Requirements

July 25, 2026

Yesterday afternoon, the Federal Aviation Administration (FAA) released a final rule that requires all legacy aircraft equipped with radio altimeters to upgrade or retrofit their altimeters to ensure they can withstand potential interference from 5G and other advanced wireless signals. Under the rule, the FAA required all aircraft operating under Part 121 or Part 129 to meet the new requirements no later than December 30, 2030. All other aircraft equipped with radio altimeters that operate under Part 91 must comply with the same requirements no later than October 31, 2034.

In a related action on Friday, the Federal Communications Commission (FCC) issued its Report and Order (R&O) that outlines the rules for auctioning the newest 5G wireless spectrum band—known as the Upper C-Band—to telecommunications companies before July 2027. There are two notable inclusions in the R&O. First, the FCC created a radio altimeter rebate program that will allow proceeds from the spectrum auction to reimburse aircraft owners and operators the cost to install new altimeters. Second, the FCC will require companies that successfully bid on the Upper C-Band spectrum to implement safeguards that ensure their use of the band and transmissions do not interfere with radio altimeters and aviation safety.

AAAE has engaged with the FAA and industry stakeholders to ensure that the growing use of 5G and other advanced wireless signals does not interfere with aviation safety or negatively impact airport operations. Based on comments from airline organizations, we expect that the air carriers will be able to comply with the retrofit deadlines established by FAA’s final rule, especially given the financial incentives created by the FCC’s new rebate program. Nevertheless, AAAE will continue to monitor the ongoing transition and retrofit effort to mitigate potential impacts on airport operations and aviation safety.

Background. For years, AAAE has engaged with FAA to address concerns over the potential interference of wireless signals with radio altimeters in aircraft in order to mitigate possible operational disruptions at airports. In 2022, Verizon, AT&T, and other companies took steps to deploy their 5G networks in the 3.70–3.98 GHz frequency band (known as the Lower C-Band). FAA and the aviation community raised concerns that the networks in the Lower C-Band could negatively interfere with radio altimeters, which use signals in the nearby 4.2–4.4 GHz frequency band (known as the RA Band). Ultimately, the telecommunications companies agreed to implement measures to mitigate potential interference through January 2028.

Spectrum Auction Requirement. In July 2025, under the One Big Beautiful Bill Act (OBBBA) of 2025, Congress required the FCC to auction spectrum in the 3.98–4.2 GHz frequency band (known as Upper C-Band), which is intended to be used by telecommunications companies in a similar manner as the Lower C-Band. At the same time, however, FAA raised concerns that wireless signals from the Upper C-Band and Lower C-Band (when the voluntary mitigation measures cease in 2028) pose a risk of interfering with radio altimeters, with signals from the Upper C-Band being more problematic because of their adjacency to the RA Band.

FAA’s Proposed Rule on Retrofit Requirements. In January, to address concerns from an auction of spectrum in the Upper C-Band, the FAA proposed a rule that would have required all radio altimeters on aircraft to meet minimum performance requirements that ensure the equipment can withstand wireless signals from both the Upper C-Band and Lower C-Band. Any aircraft operating under Part 121 or Part 129 would have to meet the new requirements by the date the FCC authorizes wireless services in the Upper C-Band. All other aircraft with radio altimeters would have to comply within two years after the deadline applicable to aircraft operating under Part 121 and Part 129.

In March, AAAE submitted comments to the FAA’s proposed rule. We expressed support for a permanent solution that allows advanced wireless networks, such as 5G, to safely co-exist with aviation and that does not negatively impact airport operations. To achieve that goal, we urged the FAA to establish reasonable deadlines for operators to retrofit their radio altimeters, recognizing that significant certification, production, and logistical challenges exist in order to complete the transition. AAAE also encouraged the FAA to work with the relevant telecommunications companies to ensure that current mitigation measures remain in place until such time as air carriers can upgrade their aircraft.

FAA Final Rule and FCC R&O. In the final rule and R&O, the FAA and FCC repeatedly emphasized the significant amount of coordination that occurred between the agencies to ensure that (a) the Upper C-Band spectrum auction does not negatively impact aviation safety and (b) the appropriate mitigation measures will be implemented by the telecommunication companies that successfully bid on the spectrum. Collectively, the final rule and order establish the following timeline for the auction and retrofitting of radio altimeters in all legacy aircraft:

Updated Performance Standards for Radio Altimeters: Under its final rule, the FAA confirmed that the agency expects standards for the next generation of radio altimeters to be released in March 2027. Once released, manufacturers will be able to obtain the necessary approvals for their C-Band-resistant altimeters to be installed in aircraft.
Upper C-Band Spectrum Auction: Under the OBBBA, the FCC must complete the auction for the Upper C-Band spectrum no later than July 4, 2027. Based on the R&O released today, the FCC is on track to meet the deadline established by Congress. A specific date, however, has not yet been set for the auction.
Availability of Funds in Rebate Program: Within 6 to 12 months after the auction occurs, funding is expected to become available for the FCC’s radio altimeter rebate program. Once funding is available, aircraft owners and operators that install the appropriate radio altimeters can obtain a lump-sum payment to defray the costs of the upgrade.
Installation and Retrofit Deadline: Under its final rule, FAA required all aircraft operating under Part 121 or Part 129 to meet the new radio altimeter requirements no later than December 30, 2030. All other aircraft equipped with radio altimeters that operate under Part 91 must comply with the same requirements no later than October 31, 2034.
Authorization of Wireless Services in Upper C-Band: Under the FCC’s R&O, the companies that successfully bid on the spectrum auction may begin providing wireless services in the Upper C-Band in the top 75 metropolitan areas on December 31, 2030. These services may be expanded to all remaining markets beginning July 30, 2031.