FAA’s Supersonic Overland Plan Faces Technical Questions Over Sonic-Boom Standard
AeroMorning – John Smith – August 26, 2026
A proposed FAA rule could reopen US airspace to civil supersonic flight, but the framework is already facing technical criticism over its noise metric, the scientific basis of its proposed limit and the practical limitations of Mach Cutoff Operations. The outcome could be particularly important for US programs such as Boom’s Overture and Spike Aerospace’s S‑512.
A new framework for supersonic flight
On July 2, 2026, the FAA published a proposal to enable overland supersonic flight. It would replace the speed‑based ban with a performance‑based system under which operations are permitted if boom effects at the surface remain below a specified limit.
The proposed standard is a maximum peak sonic‑boom overpressure of 0.11 psf at the surface. Operators would demonstrate compliance using an FAA‑approved method based on measurement, modeling or another acceptable means. The proposal covers both primary and secondary booms.
The FAA also identifies Mach Cutoff Operations (MCO) as a possible technique: by selecting an appropriate combination of altitude and Mach number under specific atmospheric conditions, the boom can refract back into the atmosphere rather than reaching the ground at significant intensity.
This approach regulates the effect at the surface rather than simply the aircraft’s speed.
1. Does peak overpressure adequately represent perceived noise?
Peak overpressure is useful to describe shock strength, but it does not directly represent how people perceive the event on the ground. Waveform shape and duration, frequency content and rise time affect human response.
NASA has investigated perception‑based metrics such as PLSEL because peak pressure alone does not capture all acoustic characteristics. Conventional noise certification uses metrics like EPNL (in EPNdB), which account for frequency, duration and tonality.
2. Where does the 0.11 psf limit come from?
Environmental groups including Earthjustice and the Sierra Club argue the FAA has not shown that 0.11 psf provides an acceptable exposure level for communities. They also question whether peak overpressure captures human perception adequately. A level technology can achieve is not necessarily proven acceptable to the public. The proposal acknowledges the need for more research, including insights expected from NASA’s Quesst/X‑59 program.
3. The Mach Cutoff problem: can it be followed over a complete route?
Mach cutoff is not a fixed speed; it varies with altitude and atmospheric conditions. ALPA questions whether MCO can be maintained throughout an entire commercial flight. The aircraft would need to determine the applicable cutoff condition and continuously adjust speed and/or altitude.
The technical issue is whether changes can be predicted accurately and far enough in advance to remain supersonic while staying within the MCO envelope. If conditions force sub‑useful speeds or frequent altitude changes, commercial benefit erodes.
4. Atmospheric variability adds another layer of uncertainty
Sonic‑boom propagation is highly sensitive to the atmosphere. Temperature gradients, winds and layering can alter propagation and refraction. A condition predicted benign under one profile may behave differently under another.
5. Boom Overture: an opportunity rather than a prerequisite
The rule could benefit Boom’s Overture, designed to cruise at Mach 1.7 with 64–80 passengers. Boom has focused on over‑water supersonic segments and near‑Mach‑1 over land, so the rule is not a prerequisite. It could expand commercially attractive routes by allowing supersonic segments over suitable US territory, provided noise requirements are met. Transcontinental routes like New York–Los Angeles could see meaningful time savings. Boom has targeted 2029 for entry into service.
