The FAA no longer wants to police speed. It wants to police what hits the ground. A notice of proposed rulemaking published around 30 June would rewrite 14 CFR 91.817, the 1973 ban that treated anything above Mach 1 over land as forbidden unless the Administrator issued a special flight authorisation. The replacement is an interim, performance-based test. An aircraft could fly supersonic over the United States if sonic-boom overpressure at the surface stays at or below 0.11 pounds per square foot, if the operator shows that with measurement, modelling or another FAA-approved method and if it flies under any limits the Administrator writes. Concorde put about 1.94 psf on the ground at Mach 2 and 52,000 feet. Eleven-hundredths of a pound is the difference between a window-rattling crack and a wave that may not even be noticed. The rule is not final. Comments closed in mid-August. Landing-and-takeoff noise is a separate thing. The agency has talked about finishing both tracks by mid-2027. Until those pieces exist, this is a door.
NASA’s X-59 is the flying argument for that number. The Lockheed Martin needle-nose, built for the Quesst mission, first flew on 28 October 2025, went supersonic on 5 June and reached its design cruise of Mach 1.4 and 55,000 feet a week later. Flight 25 left Armstrong on 21 August, lasted 72 minutes and flew about Mach 1.2 at roughly 49,000 feet. Flying qualities, loads and stability have tracked the models. That is the easy half. The chase F-15 still lays its own boom over the desert, so the X-59’s signature has not yet been isolated. The mission that matters is the acoustic campaign, community overflights that ask whether an elongated fuselage can turn a boom into a thump like a distant car door. Those data are what ICAO and foreign regulators will actually read. A laboratory Mach number does not reopen New York-Los Angeles. A measured overpressure that people accept might.
Boom’s XB-1 already showed Mach cutoff, shock waves bending upward before they reach the surface. Overture is sold as a Mach 1.7 airliner that would live or die on that physics plus engines that do not exist in certified form, fuel burn that passengers will pay for, and airport sideline noise that the 0.11 psf cruise rule does not cover. The FAA text is honest about the sequence. En-route quiet boom first. Then LTO. Then operations without a one-off waiver. That is why the bottleneck is moving, not disappearing. A company can clear 0.11 psf on a test day and still fail on takeoff noise, spare engines, insurance, slots and a public that remembers Oklahoma City. The Concorde era does not restart because a speed ban is rewritten. It restarts if X-59’s thump survives contact with houses, if Boom and anyone else can certify an engine and a business case and if airports will accept a slender fast jet that still has to start and stop like every other airliner. Until those three tests are public, America has a proposed noise number and a research aircraft with 25 flights. That is progress. It is not yet a ticket.