The Federal Aviation Administration published a notice of proposed rulemaking titled Requirements for Interference-Tolerant Radio Altimeter Systems in the Federal Register on January 7, 2026. This proposed rule establishes new minimum performance standards for radio altimeters to ensure safe aviation operations amid wireless signals in the Upper C-band.
The directive stems from Section 40002 of the One Big Beautiful Bill Act, signed into law in July 2025. This legislation directs the Federal Communications Commission to complete competitive bidding for at least 100 megahertz in the 3.98-4.2 gigahertz band. To accommodate these wireless services, the Federal Aviation Administration requires altimeters to withstand interference from neighboring spectrum bands while continuing to provide accurate altitude readings to pilots and integrated aircraft safety systems.
Compliance timelines depend on the type of aircraft operation. Aircraft operating under part 121, and part 129 aircraft with 30 or more passenger seats or a payload capacity exceeding 7,500 pounds, must meet the new performance requirements by the date the Federal Communications Commission authorizes wireless services in the Upper C-band. All other aircraft equipped with radio altimeters must comply with the same standards two years later.
The proposed rule affects operating rules under Title 14 of the Code of Federal Regulations, specifically parts 91, 121, and 129. The Federal Aviation Administration determined that these minimum interference tolerance requirements reflect the best achievable interference rejection using current technology without compromising system performance.
This action serves as a companion to the Federal Communications Commission’s notice of proposed rulemaking to expand the ecosystem for next-generation wireless services in the 3.7-4.2 gigahertz band. The Federal Communications Commission aims to make as much as 180 megahertz, and at least 100 megahertz, of the Upper C-band available for terrestrial wireless flexible use.
Stakeholders may submit comments on this proposal by March 9, 2026. The proposal is docketed under FAA-2025-5666, Notice No. 26-02.
Summary written for CheckAero from the official document. It is not legal advice; read the full text before acting.