Civil supersonic flight over U.S. land has been illegal since 1973. The FAA proposes lifting that ban for aircraft that keep ground-level sonic boom overpressure at or below 0.11 psf.
Approval is aircraft-specific, not categorical, and the agency hasn’t specified a compliance method.
For fifty years, the rule was simple. Fly civil aircraft faster than Mach 1 over U.S. land and you’re in violation.
No hearing, no variance, no demonstration required. The 1973 regulation didn’t care how quiet your aircraft was — speed alone triggered the prohibition.
The proposed rewrite flips that logic. Speed becomes legal. Noise becomes the regulated quantity, measured in pounds per square foot of overpressure at the surface.
That sounds like a technical fix, but it’s actually a structural change in how approval works: the category disappears, and each airframe gets judged on its own sonic footprint.
A speed ban becomes a boom ceiling
The 0.11 psf number is the headline. Under the proposed rule, as summarized by Baker Botts, civil aircraft may exceed Mach 1 over land only when sonic boom overpressure at the surface stays at or below 0.11 psf. That’s about twenty times below the 1.94 psf cruise boom Concorde typically produced, a pulse still strong enough to rattle windows and draw thousands of complaints in U.S. test campaigns.
The old rule — in force since April 27, 1973 — barred civil aircraft from overland supersonic flight outright. Executive Order 14304 directed the FAA to repeal the prohibition and establish interim noise-based standards.
The proposed standard also captures secondary booms — indirect sonic booms that may reach the surface — alongside primary booms. That’s a broad net. An aircraft can’t just tune its primary boom signature and call it done; every overpressure path to the ground counts.
The verification gap the FAA hasn’t closed
The FAA splits compliance into two concepts. The method is how an operator proves the aircraft can stay under 0.11 psf during validation — measurement, modeling, or “other methods.” The means is the operational plan to keep any stronger overpressure from reaching people along the route.
The rule doesn’t prescribe either; an operator submits a proposal and the FAA Administrator approves it or not. That’s the entire framework.
This is the unresolved throughline. Will the agency accept pure computational modeling for an aircraft that doesn’t exist yet? Will it require flight-test measurements?
If measurement is required, who pays for the instrumentation and where does testing happen?
There’s a structural wrinkle here, too. You can’t legally fly supersonic over land to collect measurement data for a certification that would let you fly supersonic over land. Modeling becomes the de facto starting point for most programs — whether the FAA formally blesses that path or not.
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One federal ceiling, several local floors
Passing the federal 0.11 psf test doesn’t get you into every airport corridor. California sets a different threshold: 65 dB CNEL as the maximum community aircraft noise level around airports. Airports exceeding that standard must fix the problem or secure a variance — independent of any FAA supersonic certification.
The FAA’s Part 150 noise compatibility program adds another layer: once an airport’s noise compatibility program is approved, it commonly produces binding local limits — curfews, preferential runway assignments, caps on noisy operations. A supersonic aircraft could clear the federal boom standard and still be barred from overnight departures wherever a curfew or noise cap applies.
The result would be a patchwork. One aircraft, one federal approval, and a map of local restrictions that differ airport by airport. Travelers may find certain corridors simply absent from the route map — not because the aircraft failed the federal test, but because a single airport said no.
Four programs, one measurable number
NASA’s X-59 is the only program with a published ground loudness target — about 75 PLdB — attached to a regulatory research mission. Spike Aerospace advertises 70–75 PLdB for the S-512, but that figure is a marketing claim. Boom and Exosonic publish no numerical boom targets, so the table below is thinner than press releases suggest.
| Program | Developer | Current status | Published boom target (psf or PLdB) | Stated compliance method focus | Published cost/timeline data |
|---|---|---|---|---|---|
| X-59 QueSST | NASA / Lockheed Martin | Low-boom flight demonstrator designed to produce a shaped sonic thump. | Shaped boom of about 75 PLdB at ground level; no official psf figure. | Low-boom shaping; not tied to FAA’s 0.11 psf method. | Research demonstrator; no certification timeline or cost figure published. |
| Spike S-512 Diplomat | Spike Aerospace | Private supersonic business-jet program under development. | Under about 70–75 PLdB; no official psf conversion provided. | Proprietary low-boom design; relies on design and modeling. | No regulator-verified certification date or cost figure published. |
| Boom Overture (future airliner) | Boom Supersonic | Commercial supersonic airliner concept under development. | No definitive public psf or PLdB target for routine service. | Low-boom design ambitions; no published regulatory approach. | No approved certification schedule. |
| Exosonic passenger concept | Exosonic | Early-stage developer of a proposed low-boom supersonic airplane. | No numerical ground overpressure or PLdB target specified. | Stresses aerodynamic shaping and low-boom design; no published regulatory approach. | No regulator-anchored certification timelines or cost figures disclosed. |
The table’s deeper problem is in the fourth column: the programs that publish numbers speak in PLdB, while the FAA’s proposed limit is in psf. Those metrics don’t convert cleanly—regulators write standards in pounds per square foot, manufacturers market in perceived loudness, and that gap is where certification disputes will live.
Airport upgrades deferred, not decided
Cruise-phase noise standards and separate takeoff and landing rules remain unwritten; ICAO’s new supersonic landing-and-takeoff noise standard takes effect from 2029. The takeoff/landing piece matters because supersonic aircraft may require airport infrastructure changes and added noise monitoring before they can operate from many airports. Who bears those costs hasn’t been settled, and for route viability that question may decide where supersonic flights can land.
Why the old international approach never set a ceiling
The 1973 rule had a specific origin: NASA’s account points to opinion surveys in cities where military jets made repeated supersonic passes, and to resident complaints about rattled windows and feared structural damage. That’s the visceral record every regulator now carries forward.
For decades, the international framework didn’t do much better. ICAO Annex 16 Volume I Chapter 12 set no explicit boom limit; it only required later aircraft of a type to be no louder than the first certificated example. It provided no overpressure ceiling and no authorization for routine overland operation.
ICAO has since approved a new supersonic landing-and-takeoff noise standard that applies from 2029, and it is still developing an en route low-boom standard. European regulators still require specific authorization for supersonic speed over EU land and territorial waters. The FAA isn’t harmonizing against a global playbook — it’s writing one.
What changes for travelers — and what doesn’t
If you’re a Western traveler eyeing faster overland segments to Asia-Pacific hubs, don’t book anything yet: the aircraft-specific certification means only certain models will be approved for overland supersonic flight. Route availability depends on which aircraft clears the federal bar — and then which local noise limits still apply at the airports on that route.
The sequencing matters too. Cruise-phase and takeoff/landing standards are still unwritten, and the FAA hasn’t said whether compliance verification methods will come first. Operators building business cases need to know whether modeling alone passes muster, because flight-test measurement campaigns are expensive.
Federal approval won’t flip a switch at the airport gate. Which corridors open first will still depend on the airport-level curfews, runway rules, and noise caps described above. Watch for the compliance methodology document — that unglamorous PDF will determine everything else.
Questions? Answers.
Is it illegal to fly supersonic over land?
Yes. Civil supersonic flight over U.S. land has been illegal since April 27, 1973, under 14 C.F.R. §91.817. The FAA’s proposed rule would replace that speed ban with a noise-based standard, but until it’s finalized the prohibition remains in force.
What are the FAA regulations for supersonic flight?
Under the proposed rule, §91.817(a)(1) would limit ground-level sonic boom overpressure to 0.11 psf. Section 91.817(a)(2) would require operators to demonstrate — through an FAA-approved method — that primary and secondary sonic booms stay under that ceiling and that safeguards prevent stronger overpressure from reaching the surface.
Can you fly supersonic as a civilian?
Not over U.S. land today. Under the FAA’s proposed rule, civilians would be able to fly supersonic over land only in aircraft that demonstrate their ground-level boom stays at or below 0.11 psf. Executive Order 14304 directed the FAA to repeal the old ban and establish this interim standard.
Why were supersonic flights banned?
The 1973 ban was strongly influenced by public opinion surveys in cities where military jets flew repeated supersonic runs. Many residents complained about window rattle and potential damage. NASA’s historical account ties those complaints directly to the regulation that took effect on April 27, 1973.
