Carriers and private aircraft operators from the United States will be required to invest an estimated USD4.49 billion to upgrade existing radio altimeters to next-generation, interference-tolerant units, according to a Federal Aviation Administration (FAA) estimate. The initial deadline for the retrofit programme is expected to fall between 2029 and 2032.

The proposed rule was issued in response to the One Big Beautiful Bill Act of 2025, a flagship Donald Trump’s legislative package, which directed the Federal Communications Commission (FCC) to expand next-generation wireless services by auctioning at least 100 megahertz of spectrum in the Upper C-band.

Under the proposal, all radio altimeters would be required to withstand interference from wireless signals in adjacent spectrum bands while continuing to provide accurate altitude data to pilots and integrated aircraft safety systems.

The regulation would apply to all aircraft equipped with radio altimeters operating under Parts 91 and 121, as well as to Part 129 aircraft with 30 or more passenger seats or a payload capacity exceeding 7,500 pounds (3,401 kilogrammes), and Part 135 aircraft.

Part 121 and 129 aircraft would be required to transition to compliant equipment between 2029 and 2032. All other aircraft fitted with radio altimeters would be granted an additional two years to comply.

The earlier compliance date for Part 121 and 129 operations was set because “they constitute flights by the major domestic and international airlines and affect the majority of the flying public, have the highest public expectation of safety, and are the most critical to the national economy,” said the agency.

The FAA estimates that retrofit costs will amount to USD1.58 billion for Part 91 operators, USD1.36 billion for Part 121 operators, USD891 million for Part 129 operators, and USD651 million for Part 135 operators. Annualised costs are projected to range between USD61 million and USD150 million over a 20-year period, excluding indirect costs such as aircraft downtime, supply-chain constraints, and other potential disruptions.

According to the agency, approximately 40,871 aircraft will require modification, involving the replacement or upgrade of at least 58,579 radio altimeters. Almost 14,000 operators are currently registered in the United States under Parts 91, 121, 129, and 135.

Bloomberg reported that the FCC was considering ways to help cover the costs of the retrofits, including through proceeds from its auction.