The X-59, officially nicknamed “Quesst,” is a one-of-a-kind experimental aircraft built by Lockheed Martin’s Skunk Works division for NASA with a single ambitious goal: prove that a supersonic plane can be designed to produce a soft thump on the ground instead of the jarring double-bang of a traditional sonic boom. The aircraft completed its first flight in May 2024 at Lockheed Martin’s facility in Palmdale, California, and is now working through an expanding flight-test campaign. If the X-59 delivers on its promise, the data it generates could convince international regulators to lift the decades-old ban on supersonic flight over land, reopening a chapter of commercial aviation that effectively closed with the Concorde.
Why Sonic Booms Have Kept Supersonic Flight Grounded
Every object moving faster than the speed of sound generates shock waves that merge and travel to the ground as a sonic boom. The Concorde’s boom was loud enough to rattle windows and startle people miles from its flight path, and by the early 1970s, the FAA had banned all civil supersonic flight over the continental United States. Most other aviation authorities followed. That rule has stood for over fifty years, and it applies regardless of how loud the boom actually is. There is no “acceptable boom” threshold in current regulations because, until recently, nobody had built a full-scale aircraft specifically shaped to make that threshold worth discussing. The X-59 exists to fill that gap.
How the X-59 Tames the Boom
A conventional supersonic aircraft’s boom is produced when shock waves generated at various points along the fuselage, wings, and engines coalesce into two strong pressure fronts, an N-wave, that reach the ground almost simultaneously. The result is a sharp, startling pair of bangs. The X-59’s entire airframe is sculpted to prevent those shocks from merging. Its nose stretches nearly a third of the aircraft’s total length, tapering to a fine point so that the initial pressure rise builds gradually rather than slamming the air all at once. The canopy sits well aft and blends smoothly into the fuselage to avoid creating its own discrete shock. The wings are swept and carefully contoured, and the single General Electric F414 engine is mounted on top of the aft fuselage, tucking its inlet and exhaust shocks above the aircraft where they have less chance of reinforcing the waves heading earthward.
The net effect is that the distinct pressure spikes spread out in time as they travel to the ground, arriving as a series of gentle pressure changes rather than one explosive N-wave. NASA’s target for the perceived sound on the ground is roughly 75 PLdB, a unit that accounts for how human ears respond to impulsive noise. For comparison, a conventional supersonic boom typically registers around 105 PLdB. The difference is dramatic: 75 PLdB is closer to the sound of a car door closing down the street than to a thunderclap overhead.
An Aircraft With No Forward Windshield
That long, slender nose creates a design problem any pilot would notice immediately: you cannot see forward. The X-59 has no traditional windshield. Instead, NASA and Collins Aerospace developed the eXternal Vision System, or XVS, a suite of high-definition cameras and a terrain database fused into a real-time display mounted where the forward window would normally be. The system gives the pilot a synthetic view of the airspace ahead, overlaid with live camera imagery, so takeoffs, landings, and in-flight maneuvering work much the way they would with a conventional canopy. The concept was tested extensively in simulators and chase-plane exercises before the X-59 ever left the ground.
This camera-based cockpit is not just a workaround for the X-59’s unusual shape. It represents a broader shift in how experimental and even commercial aircraft might handle forward visibility in the future. High-speed aircraft designed for low drag benefit from smooth, unbroken fuselage lines, and replacing a heavy, structurally complex windshield with cameras and displays saves weight while allowing designers far more freedom in shaping the nose.
What the X-59 Looks Like by the Numbers
The aircraft is about 99.7 feet long (just over 30 meters) with a wingspan of roughly 29.5 feet. It is designed for a cruise speed of Mach 1.4, or about 925 miles per hour, at an altitude of around 55,000 feet. It carries no passengers and no weapons; this is purely a research platform. The single F414 engine, a variant of the powerplant used in the F/A-18E/F Super Hornet, provides enough thrust for sustained supersonic cruise but keeps the aircraft relatively small and manageable for a test program that will eventually involve dozens of flights over populated areas. The aircraft weighs roughly 32,300 pounds at maximum takeoff weight, making it lighter than a typical business jet.
Modeling the Boom Before It Hits the Ground
Before the X-59 flies over communities, NASA needs to know exactly what the sound footprint will look like on the ground under varying weather conditions, altitudes, and flight paths. The agency uses computational fluid dynamics to simulate the pressure field near the aircraft in supersonic cruise and then propagates that data to the ground with a tool called PCBoom, which traces acoustic rays through the atmosphere. Published research describes this workflow: near-field pressure data from NASA’s FUN3D solver is fed into PCBoom, which solves a specialized equation along those rays to predict what observers on the ground will hear.1Journal of Aircraft. Simulation and Regression Modeling of NASA’s X-59 Low-Boom Carpets Across America
These simulations produce what researchers call “boom carpets,” maps of predicted sound levels laid across the terrain beneath a flight path. The shape and intensity of a boom carpet depend on the aircraft’s altitude, speed, heading, and the atmospheric conditions between the plane and the ground. Temperature gradients, wind shear, and humidity all bend and attenuate the shock waves in complex ways. Atmospheric turbulence is one variable that is especially hard to pin down. On average, turbulence tends to reduce the loudness of sonic booms as it scatters and diffuses the shock fronts, but it can also focus energy in unpredictable ways, occasionally producing louder-than-expected levels at specific locations.2JASA Express Letters. Estimating the noise dose range of the NASA X-59 aircraft in supersonic cruise using PCBoom propagation simulations This uncertainty is one reason NASA plans to pair its computational predictions with extensive ground-based acoustic measurements during actual overflights.
The Community Overflight Campaign
The ultimate purpose of the X-59 is not just to prove that a quiet supersonic airplane can be built. It is to generate enough rigorous data on how real communities respond to its sound that regulators can write new rules. NASA’s plan, called the Quesst community survey campaign, involves flying the X-59 repeatedly over several selected U.S. cities and collecting survey responses from residents beneath the flight path. During each survey period, a sample of residents will be recruited in advance and asked to fill out a brief survey each time the aircraft flies over, roughly 80 times throughout a month-long window.3NASA Technical Reports Server. Overview of A Survey Methods Test for the NASA Quesst Community Survey Campaign
That is a substantial ask of volunteers, and NASA has spent considerable effort figuring out how to keep them engaged. In 2023, the agency ran a month-long test of its survey methods before the X-59 was ready to fly. A sample of 800 residents was recruited from a simulated overflight area and asked about their reactions to noise from normal aircraft operations. Respondents could choose between a web survey and a smartphone app. NASA used a graduated incentive structure to encourage consistent participation and tracked response rates over time to understand how engagement drifted as the novelty wore off.4NASA Technical Reports Server. Overview of A Survey Methods Test for the NASA Quesst Community Survey Campaign Location data was also collected from respondents, because estimating each person’s individual noise exposure from the X-59 requires knowing where they were when the plane passed overhead.
The quality of these surveys matters enormously. The end product of the Quesst campaign is a dose-response curve: a statistical relationship between how loud the boom is at a given location and how annoyed residents report being. Research into the design of these surveys has explored what happens when errors creep into the dose estimates, finding that even modest inaccuracies in estimating the noise level at each person’s location can shift the apparent annoyance relationship in ways that matter for regulatory decisions.5INTER-NOISE and NOISE-CON Congress and Conference Proceedings. Dose error impacts on a collection of realistic dose-response curves based on a NASA sonic boom community noise survey Variability in individual sensitivity, participation rates, and the inherent randomness of atmospheric conditions on any given flyover day all add uncertainty. Getting the dose right is as important as getting the response right.
Who Decides Whether Supersonic Flight Over Land Becomes Legal
The X-59’s data is ultimately aimed at two regulatory bodies. Within the United States, the FAA has maintained its ban on civil supersonic flight over land since 1973. Internationally, the International Civil Aviation Organization (ICAO) sets noise standards that member nations use as the basis for their own rules. Neither body currently has an acceptable noise standard for supersonic overland flight because, until the X-59, there was no aircraft capable of producing a boom quiet enough to test whether the public would tolerate it. The Quesst campaign is designed to hand those regulators something they have never had: a scientifically defensible dataset linking a specific level of supersonic noise to a measured level of community annoyance.
If the data shows that residents exposed to the X-59’s quiet boom report annoyance levels comparable to what they experience from ordinary subsonic air traffic, regulators would have a strong basis for establishing a noise ceiling that permits supersonic overland flight, at least for aircraft that meet a specific boom standard. If, on the other hand, even the X-59’s muted thump proves persistently bothersome across multiple communities, the path to regulatory change gets much longer and harder. The program’s value lies in providing an answer either way, replacing decades of speculation with evidence.
What the X-59 Is Not
It is worth being clear about what the X-59 will not do. It is not a prototype for a commercial airliner. It carries no passengers, has no cabin, and is not designed for the range, payload, or economics of airline service. Several private companies are working on supersonic business jets and small airliners, but those programs face their own engineering and certification challenges beyond just the boom. The X-59’s contribution is narrower and, in some ways, more consequential: it is a flying rule-change machine. Its job is to produce the scientific basis for new noise regulations. The companies building supersonic transports need those regulations to exist before their aircraft can legally operate over land. Without the X-59’s data, the regulatory conversation has no foundation.
The aircraft also is not designed to break speed records or push the boundaries of supersonic performance. Mach 1.4 is modest by military standards and well below the Concorde’s Mach 2.04 cruise. The choice of speed is deliberate: it is fast enough to be genuinely supersonic and representative of the speeds a future commercial aircraft might use on overland routes, while keeping the engineering focused on boom shaping rather than high-Mach thermal and structural challenges.
Ground Recording Systems and Flight Validation
Alongside the community surveys, NASA is investing heavily in ground-based acoustic measurement. Recording a sonic boom accurately is harder than it might sound. The pressure signature arrives as a very brief, impulsive event, and capturing it faithfully requires microphones and recording systems with specific frequency response and dynamic range characteristics. Ground conditions also matter: reflections off pavement, buildings, and terrain can distort the waveform. NASA has conducted supersonic flight tests specifically to evaluate and refine the ground recording systems that will be deployed beneath X-59 flight paths, ensuring that the measured boom levels match what the computational models predict and that the acoustic data is trustworthy enough to underpin regulatory decisions.
These ground arrays typically consist of microphone stations spread over a wide area beneath the expected boom carpet. By comparing the measured pressure signature at each station with the prediction from the PCBoom propagation model, researchers can validate and calibrate the simulation tools. Where the predictions and measurements diverge, the atmospheric and terrain variables that caused the mismatch can be studied, improving future predictions for different cities and different weather conditions.
Why Atmospheric Conditions Keep Things Uncertain
Even with an aircraft perfectly shaped to minimize the boom, the atmosphere has the final say on what people hear. Sonic boom propagation is sensitive to temperature profiles, wind speeds and directions at multiple altitudes, and humidity. A temperature inversion can bend shock waves back toward the ground more steeply, intensifying the boom in unexpected places. Wind shear can shift the boom carpet sideways so that areas expected to be quiet receive a louder signal, and vice versa.
Turbulence adds another layer. Small-scale atmospheric turbulence scatters the shock waves as they descend, and the effect is statistical rather than predictable for any single flight. On average, this scattering weakens the boom, but for any given pass, a listener on the ground might experience a noticeably louder or quieter event than the average prediction.6JASA Express Letters. Estimating the noise dose range of the NASA X-59 aircraft in supersonic cruise using PCBoom propagation simulations This variability is one reason the Quesst campaign involves many flights over each community rather than just a handful. A single quiet pass on a calm day tells you little about how annoying the sound will be across a month of diverse weather. The statistical power comes from accumulating enough observations under enough atmospheric conditions that the dose-response relationship reflects real-world experience, not cherry-picked conditions.
The Broader Landscape of Supersonic Ambitions
The X-59 is flying at a moment when multiple companies are pursuing supersonic commercial aircraft. Boom Supersonic has been developing the Overture, a Mach 1.7 airliner designed for transoceanic routes where overland boom restrictions do not apply, with plans to eventually benefit from any new overland regulations the X-59 might help create. Spike Aerospace has proposed a low-boom supersonic business jet. Exosonic has explored concepts for quiet supersonic aircraft designed from the start around overland routes. All of these efforts exist downstream of the regulatory question that the X-59 is trying to answer.
The economics of supersonic travel remain challenging even if the boom problem is solved. Supersonic aircraft burn more fuel per passenger-mile than subsonic ones, which raises both cost and carbon-emission concerns. Sustainable aviation fuel and more efficient engine designs could help close that gap, but nobody expects supersonic tickets to be cheap. The initial market is widely expected to be business-class and premium travelers on routes where time savings justify the price premium. Whether that market is large enough to sustain an aircraft program is a question the X-59 cannot answer, but it can remove the single biggest regulatory barrier standing in the way.
For the communities that will eventually hear the X-59 pass overhead during the Quesst campaign, the experience should be anticlimactic by design. If NASA’s shaping and modeling work has gone right, most people on the ground will hear something closer to a distant rumble or a soft thud than anything resembling the startling crack of a traditional sonic boom. Whether “anticlimactic” is good enough to change a fifty-year-old rule is exactly what the surveys will determine.