FAA adopts Air Force categorical exclusion for high-altitude supersonic flight testing: Top points

On August 24, 2026, the Federal Aviation Administration (FAA) published a Federal Register notice adopting a United States Department of the Air Force (DAF) categorical exclusion (CATEX) under the National Environmental Policy Act (NEPA). The CATEX covers supersonic flying operations over land and above 30,000 feet mean sea level (MSL), or over water and above 10,000 feet MSL and more than 15 nautical miles from land. The CATEX is available for the FAA’s immediate use. 

The FAA expects to use the CATEX when considering special flight authorization (SFA) applications for supersonic flight testing within those parameters. The CATEX may allow the agency to make the environmental findings required by Title 14, Section 91.818, of the Code of Federal Regulations (14 CFR § 91.818) without preparing an environmental assessment (EA) or environmental impact statement (EIS), absent extraordinary circumstances. 

The adoption appears to be the FAA’s first publicly announced use of Section 109 of NEPA through a notice in the Federal Register. It also advances the implementation of Executive Order 14304, “Leading the World in Supersonic Flight,” and complements the FAA’s pending “Enabling Supersonic Overland Flight” rulemaking, for which the comment period closed on August 17, 2026.

This alert discusses the CATEX, related environmental-review requirements, and implications for SFAs.

Background

FAA regulations prohibit the operation of a civil aircraft in the US at a true flight Mach number greater than one, except in accordance with the conditions and limitations of an authorization issued under 14 CFR § 91.818.¹ Under Section 91.818, which was adopted in a 2021 final rule that streamlined the application process, applications are submitted to the FAA’s Office of Environment and Energy and an SFA may be granted only for enumerated research and testing purposes, such as showing compliance with airworthiness requirements, determining an aircraft’s sonic boom characteristics, and measuring noise.²  

Section 91.818(c) requires the FAA Administrator to consider the potential environmental impacts of issuing each authorization under NEPA – with the applicant supplying information that describes those impacts – and Section 91.818(d) bars issuance until the FAA has taken the required action regarding those environmental findings.³ 

The two most recent published grants illustrate the scope and timing of that review. Boom Supersonic petitioned the FAA in March 2023 for authorization to conduct up to 20 supersonic test flights of the XB-1 experimental aircraft over one year within preexisting supersonic corridors at Edwards Air Force Base, at or above 30,000 feet MSL. The FAA prepared an EA, accepted public comments, and issued a finding of no significant impact (FONSI) on February 29, 2024. The SFA became effective April 7, 2024, more than a year after the petition.⁴  

Hermeus petitioned the FAA in January 2026 for authorization to conduct up to seven supersonic test flights of the Quarterhorse Mark 2.1 unmanned aircraft system over restricted airspace at White Sands Missile Range, also at or above 30,000 feet MSL. The FAA satisfied its NEPA obligations by relying on and adopting the Army’s 2010 EIS for the range and granted the SFA effective April 9, 2026 – less than three months after the petition.⁵ 

What the notice does

Against that backdrop, the August 24, 2026 notice adopts a military CATEX covering certain high-altitude supersonic flight activities.⁶ 

• The adopted CATEX. The FAA is adopting CATEX DoW A116-34, which was established by the DAF and is listed in Appendix A to the US Department of War (DOW)’s NEPA implementing procedures dated April 30, 2026. The CATEX covers “[s]upersonic flying operations over land and above 30,000 feet MSL, or over water and above 10,000 feet MSL and more than 15 nautical miles from land.”⁷ The FAA is adopting the CATEX “consistent with all substantive and procedural limitations applied by DAF.” When the DAF’s procedures require a documented CATEX determination, the FAA’s Environmental Protection Specialist will document the determination consistent with Section 1.4(f)(3) of FAA Order 1050.1G.⁸ 
  
  
• Expected use. The FAA expects to use the CATEX when considering SFA applications for supersonic flight testing over land and above 30,000 feet MSL, or over water, above 10,000 feet MSL, and more than 15 nautical miles from land.⁹ The notice identifies the DAF’s currently approved supersonic corridors at Edwards Air Force Base in California, including the Bell X-1 and Black Mountain High Altitude Supersonic Corridors and the PIRA Supersonic Corridor. It also identifies Test Area B-70, extending over Restricted Areas R-2914A through R-2915A, at Eglin Air Force Base in Florida. The FAA, however, describes its expected use of the CATEX by reference to altitude and distance-from-land parameters rather than by location.¹⁰ 
  
  
• Activities beyond SFAs. The FAA states that it may expand its use of the CATEX to “activities other than SFA applications” that fall within the CATEX’s parameters, where appropriate, and may consult with the DAF as needed.¹¹ 
  
  
• Extraordinary circumstances still apply. Before applying the CATEX to a specific action, the FAA will screen for extraordinary circumstances under its procedures in Appendix B to FAA Order 1050.1G. The FAA will also apply the DAF’s extraordinary circumstances list in Part 1.4(d) of the DOW’s procedures, including any subsequent revisions, if that list differs from the FAA’s. If an extraordinary circumstance is present, the FAA will determine whether significant effects can be avoided and will document any mitigation measures. If the CATEX cannot be applied, the FAA will prepare an EA or EIS.¹² 
  
  
• Legal basis. Section 109 of NEPA, added by the Fiscal Responsibility Act of 2023, allows a federal agency to adopt another agency’s CATEX by identifying the CATEX, consulting with the establishing agency, providing public notice of the CATEX, and documenting the adoption.¹³ The FAA and the DAF consulted between December 3, 2025 and June 29, 2026 to address the relationship between the CATEX and the FAA’s proposed actions, the extraordinary circumstances that the FAA would consider, applicable documentation requirements, and the DAF’s previous use of the CATEX – including how often the DAF modified an action or prepared an EA or EIS for an action that was otherwise covered.¹⁴ The notice appears to be the FAA’s first adoption of another agency’s CATEX announced in the Federal Register.

What the notice does not do

The adoption does not amend Sections 91.817 or 91.818. An SFA is still required for civil supersonic flight subject to those provisions, the application process remains unchanged, and applicants must continue to submit environmental information. 

The CATEX also does not cover all supersonic testing. Operations over land at or below 30,000 feet MSL, as well as operations over water at or below 10,000 feet MSL or within 15 nautical miles of land, remain outside its terms and will continue to require an EA, an EIS, or reliance on other environmental documentation. 

The CATEX does not establish categorical treatment for every action that falls within its stated parameters. An extraordinary circumstances review may result in the FAA requiring additional environmental analysis. The notice is not a rulemaking; accordingly, it did not provide a comment period, and the CATEX is available for the FAA’s immediate use.¹⁵ 

The broader supersonic agenda

Executive Order 14304, issued on June 6, 2025, directed the FAA Administrator to take necessary steps, including through rulemaking, to repeal the prohibition on overland supersonic flight in Section 91.817 within 180 days and establish an interim, noise-based certification standard. It separately directed the FAA to initiate a Part 36 rulemaking concerning supersonic noise certification, with final noise certification standards due by June 6, 2027.¹⁶  

The FAA issued the resulting Notice of Proposed Rulemaking (NPRM), “Enabling Supersonic Overland Flight,” on July 2, 2026, which would repeal the prohibition on civil aircraft operating at a true flight Mach number greater than one and permit civil supersonic flight without an SFA when the primary and secondary sonic boom overpressure at the surface does not exceed 0.11 pound per square foot, the operator obtains an FAA finding that it has demonstrated a means of complying with that standard, and the operator adheres to FAA conditions and limitations. The SFA process would remain available for testing in which sonic booms may reach the surface.¹⁷ The comment period closed on August 17, 2026 with 488 comments posted to the docket as of August 24, 2026.¹⁸ 

The adoption also follows broader changes to the NEPA framework: the Council on Environmental Quality rescinded its NEPA regulations effective April 11, 2025 and issued new CATEX guidance on April 9, 2026 addressing adoptions under Section 109; the FAA replaced Order 1050.1F with Order 1050.1G on June 30, 2025; and the DOW issued the NEPA procedures containing this CATEX on April 30, 2026.¹⁹ 

Implications

• Potential effect on flight test authorization timelines. For test campaigns that fall within the CATEX’s parameters, the NEPA component of SFA processing may be shorter than the EA-and-FONSI process the FAA used for the XB-1 authorization.
  
  
• Relevance of test profiles. Both recent SFA campaigns proposed operations at or above 30,000 feet MSL, and the CATEX covers operations above 30,000 feet MSL over land. Applicants whose proposed supersonic flight segments occur above that altitude threshold, or offshore above 10,000 feet and more than 15 nautical miles from land, align with the FAA’s stated expected use of the CATEX. Lower-altitude testing, including sonic-boom characterization near the surface, remains outside the stated parameters.
  
  
• Environmental documentation. SFA applications that address the screening criteria in Appendix B to FAA Order 1050.1G and Part 1.4(d) of the DOW’s procedures, and that support a documented CATEX determination where required, may facilitate the FAA’s environmental review process. Environmental documentation may continue to be important because CATEX determinations are subject to judicial review under the Administrative Procedure Act.
  
  
• Interaction with the pending rulemaking. If the FAA finalizes the “Enabling Supersonic Overland Flight” proposal, routine boom-free supersonic operations that satisfy the proposed surface overpressure standard would no longer require SFAs. SFAs would remain available for boom-reaching testing, and the FAA has stated that it may apply the adopted CATEX to activities beyond SFA applications. As a result, both the CATEX adoption and the pending rulemaking may be relevant to companies planning supersonic testing, certification, or operational activities during the 2026–2027 period.

Learn more

DLA Piper’s Transportation lawyers advise aircraft developers, operators, and investors on FAA and Department of Transportation regulatory matters, including special flight authorizations, environmental review, and rulemaking proceedings. DLA Piper continues to monitor developments relating to the pending supersonic rulemakings and the FAA’s use of the adopted CATEX.

For more information, please contact the authors.

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¹14 CFR § 91.817(a), https://www.ecfr.gov/current/title-14/chapter-I/subchapter-F/part-91/subpart-I/section-91.817.

²14 CFR § 91.818(a); see Special Flight Authorizations for Supersonic Aircraft, 86 Federal Register 3,782 (January 15, 2021), https://www.federalregister.gov/documents/2021/01/15/2021-00113/special-flight-authorizations-for-supersonic-aircraft.

³14 CFR § 91.818(c)–(d), https://www.ecfr.gov/current/title-14/chapter-I/subchapter-F/part-91/subpart-I/section-91.818.

⁴Petition for Authorization to Exceed Mach 1, 89 Federal Register 30,433 (April 23, 2024), https://www.federalregister.gov/documents/2024/04/23/2024-08580/petition-for-authorization-to-exceed-mach-1.

⁵Petition for Authorization to Exceed Mach 1, 91 Federal Register 18,966 (April 13, 2026), https://www.federalregister.gov/documents/2026/04/13/2026-07121/petition-for-authorization-to-exceed-mach-1.

⁶Adoption of Categorical Exclusion Under the National Environmental Policy Act, 91 Federal Register 54,783 (August 24, 2026) [hereinafter Adoption Notice], https://www.federalregister.gov/documents/2026/08/24/2026-17212/adoption-of-categorical-exclusion-under-the-national-environmental-policy-act.

⁷Adoption Notice, supra note 6, at 54,784; Department of War, National Environmental Policy Act Implementing Procedures app. A (April 30, 2026), https://www.denix.osd.mil/nepa/denix-files/sites/55/2026/05/DOW-Procedures-Combined_05252026_V1.2.pdf.

⁸Adoption Notice, supra note 6, at 54,784; Federal Aviation Administration, Order 1050.1G, National Environmental Policy Act Implementing Procedures § 1.4(f)(3) (June 30, 2025), https://www.faa.gov/documentLibrary/media/Order/FAA_Order_1050.1G.pdf.

⁹Adoption Notice, supra note 6, at 54,784.

¹⁰Id.

¹¹Id.

¹²Id. See also FAA Order 1050.1G, supra note 8, app. B; Department of War Procedures, supra note 7, pt. 1.4(d).

¹³42 USC § 4336c (added by the Fiscal Responsibility Act of 2023, Pub. L. No. 118-5, § 321(b), 137 Stat. 10, 43), https://uscode.house.gov/view.xhtml?req=granuleid:USC-prelim-title42-section4336c&num=0&edition=prelim.

¹⁴Adoption Notice, supra note 6, at 54,784.

¹⁵Id. at 54,783–84.

¹⁶Executive Order 14304, § 2, 90 Federal Register 24,717 (June 11, 2025), https://www.federalregister.gov/documents/2025/06/11/2025-10800/leading-the-world-in-supersonic-flight; see Enabling Supersonic Overland Flight, 91 Federal Register 40,470, 40,471 (July 2, 2026) [hereinafter Supersonic NPRM], https://www.federalregister.gov/documents/2026/07/02/2026-13440/enabling-supersonic-overland-flight (noting the directive to finalize noise certification standards by June 6, 2027).

¹⁷Supersonic NPRM, supra note 16, at 40,470–71.

¹⁸Id. at 40,470; Regulations.gov, Docket No. FAA-2026-6935 (last visited August 24, 2026), https://www.regulations.gov/docket/FAA-2026-6935.

¹⁹Removal of National Environmental Policy Act Implementing Regulations, 90 Federal Register 10,610 (February 25, 2025) (interim final rule); 91 Federal Register 618 (January 8, 2026) (final rule); Implementation of the National Environmental Policy Act Guidance, 91 Federal Register 18,836 (April 13, 2026), https://www.federalregister.gov/documents/2026/04/13/2026-07115/implementation-of-the-national-environmental-policy-act-guidance; Notice of Rescission of FAA Order 1050.1F, Availability of FAA Order 1050.1G, Request for Comments, 90 Federal Register 29,615 (July 3, 2025), https://www.federalregister.gov/documents/2025/07/03/2025-12362/notice-of-rescission-of-faa-order-10501f-availability-of-faa-order-10501g-request-for-comments.