The FAA has published a Notice of Proposed Rulemaking (NPRM) that would require all radio altimeter systems installed on civil aircraft to meet defined minimum performance standards designed to improve tolerance to radio frequency interference. The proposed rule is intended to ensure continued safe operation of aircraft as spectrum use near the 4.2–4.4 GHz band evolves.
The proposal stems from Section 40002 of the One Big Beautiful Bill Act, which directs the Federal Communications Commission (FCC) to allow competitive bidding for not less than 100 megahertz of spectrum in the Upper C-Band. As part of that effort, the FCC issued its own Notice of Proposed Rulemaking, In the Matter of Upper C-Band (3.98–4.2 GHz), which was published in the Federal Register on January 7, 2026. The FCC extended the comment deadline for that proceeding to February 3, 2026.
The FAA NPRM proposes minimum performance standards for radio altimeters to ensure reliable operation in an environment with increased adjacent-band wireless activity. The FAA emphasizes that stakeholder input will be critical to assessing implementation timelines, retrofit considerations, and potential operational impacts. If you have feedback on either the FCC NPRM or the FAA NPRM, please send your input to NATA by Friday, January 23, 2026.