Department of Transportation, Federal Aviation Administration: Requirements for Interference-Tolerant Radio Altimeter Systems

B-338659

September 25, 2026

The Honorable Ted Cruz
Chairman
The Honorable Maria Cantwell
Ranking Member
Committee on Commerce, Science, and Transportation
United States Senate

The Honorable Sam Graves
Chairman
The Honorable Rick Larsen
Ranking Member
Committee on Transportation and Infrastructure
House of Representatives

Subject: Department of Transportation, Federal Aviation Administration: Requirements for Interference-Tolerant Radio Altimeter Systems

Pursuant to section 801(a)(2)(A) of title 5, United States Code, this is our report on a major rule promulgated by the Department of Transportation, Federal Aviation Administration (FAA) entitled “Requirements for Interference-Tolerant Radio Altimeter Systems” (RIN: 2120-AM21). We received the rule on August 10, 2026. It was published in the Federal Register on July 31, 2026. 91 Fed. Reg. 48656. The stated effective date of the rule is September 29, 2026.

According to FAA, this rule issues new regulations that require all radio altimeters to meet specific minimum performance requirements in order to ensure safe, efficient, and reliable aviation operations in the presence of wireless signals in the C-band.

The Congressional Review Act (CRA) requires a 60-day delay in the effective date of a major rule from the date of publication in the Federal Register or receipt of the rule by Congress, whichever is later. 5 U.S.C. § 801(a)(3)(A). This rule was published in the Federal Register on July 31, 2026. 91 Fed. Reg. 48656. The Senate received the rule on August 12, 2026. 172 Cong. Rec. S4666 (daily ed. Sept. 14, 2026). The House of Representatives received the rule on August 14, 2026. 172 Cong. Rec. H5424 (daily ed. Sept. 1, 2026). The stated effective date of the rule is September 29, 2026. Therefore, the stated effective date is less than 60 days from the date of receipt by Congress.

Enclosed is our assessment of FAA’s compliance with the procedural steps required by section 801(a)(1)(B)(i) through (iv) of title 5 with respect to the rule. If you have any questions about this report or wish to contact GAO officials responsible for the evaluation work relating to the subject matter of the rule, please contact me (202) 512-8156.

Shirley A. Jones
Managing Associate General Counsel

Enclosure

cc: Kim L Young
Manager, Legal Litigation and Support
Federal Aviation Administration

ENCLOSURE

REPORT UNDER 5 U.S.C. § 801(a)(2)(A) ON A MAJOR RULE
ISSUED BY THE
DEPARTMENT OF TRANSPORTATION,
FEDERAL AVIATION ADMINISTRATION
ENTITLED
“REQUIREMENTS FOR INTERFERENCE-TOLERANT RADIO ALTIMETER SYSTEMS”
(RIN: 2120-AM21)

(i) Cost-benefit analysis

The Department of Transportation, Federal Aviation Administration (FAA) prepared an analysis of the costs and benefits of this rule. 91 Fed. Reg. 48656, 48677–48691 (July 31, 2026). In terms of benefits, FAA stated that the rule would limit the risk of inaccurate or missing height above terrain data, allowing air transportation operations to continue at their current tempo and safety environment. Id. at 48684. The FAA estimated the expected undiscounted total cost of the rule’s requirement to replace radio altimeter systems for civil fleets to range from $4.82 billion to $7.13 billion. Id. at 48685.

(ii) Agency actions relevant to the Regulatory Flexibility Act (RFA), 5 U.S.C. §§ 603–605, 607, and 609

FAA prepared a Final Regulatory Flexibility Analysis. 91 Fed. Reg. at 48692.

(iii) Agency actions relevant to sections 202–205 of the Unfunded Mandates Reform Act of 1995, 2 U.S.C. §§ 1532–1535

FAA determined the rule will not result in the expenditure of $193,000,000 or more ($100,000,000 adjusted for inflation using the most current Implicit Price Deflator for the Gross Domestic Product) by state, local, or Tribal governments, in the aggregate, or the private sector, in any one year. 91 Fed. Reg. at 48695.

(iv) Other relevant information or requirements under acts and executive orders

Administrative Procedure Act, 5 U.S.C. §§ 551 et seq.

On January 7, 2026, FAA published a proposed rule. 91 Fed. Reg. 459. FAA stated that it received 50 comments on the proposed rule on a broad range of topics. 91 Fed. Reg. at 48661. FAA responded to comments in the rule. Id. at 48661–48677.

Paperwork Reduction Act (PRA), 44 U.S.C. §§ 3501–3520

FAA determined there is no new requirement for information collection associated with the rule. 91 Fed. Reg. at 48695.

Statutory authorization for the rule

FAA promulgated this rule pursuant to section 106(f) of title 49, United States Code.

Executive Order No. 12866 (Regulatory Planning and Review)

FAA stated that the Office of Management and Budget has determined the rule is a significant regulatory action. 91 Fed. Reg. at 48678.

Executive Order No. 13132 (Federalism)

FAA determined the rule will not have a substantial direct effect on the states, or the relationship between the Federal Government and the states, or on the distribution of power and responsibilities among the various levels of government, and, therefore, will not have federalism implications. 91 Fed. Reg. at 48696.