On January 5, 2026, the FAA published a Notice of Proposed Rulemaking (NPRM) that sets forth new proposed requirements for radio altimeters and a compliance deadline for operators to retrofit their aircraft. The FAA indicated that this rulemaking is in response to the expected expansion of future wireless services in the Upper C-band, as reflected by the Federal Communications Commission’s (FCC) statutory requirement from The One Big Beautiful Bill Act of 2025, Public Law 119-21, signed on July 4, 2025, to auction at least 100 MHz in the Upper C-band by July 4, 2027.
Most notably, the rule contains two compliance deadlines. The initial performance deadline is for 14 CFR part 121 and part 129 where the aircraft has 30 or more passenger seats or a payload capacity of more than 7,500 pounds. The initial performance deadline is yet unspecified, but likely will occur between 2029 and 2032 to coincide with the FCC's date of authorization of new wireless services in the Upper C-band. The second deadline is proposed to take place two years after the initial date, applicable to all other operators that are required to equip. The rule is geographically limited to the 48 contiguous United States and the District of Columbia.
The rule’s new minimum performance requirements for radio altimeters, set forth in proposed § 91.220, are contained in a table that shows the proposed minimum radio altimeter system interference tolerance requirement applicable to different frequency ranges. The radio altimeter system would be required to operate at an altitude of 0-500 feet above ground level in this proposed interference environment.
The FAA is accepting comments on the proposed rule for 60 days. Comments are due on or before March 9, 2026.
