Level 1 - Absolute Beginner

NASA has a special new airplane. It is called the X-59. This airplane can fly very fast. It will soon fly faster than the speed of sound. This is called supersonic flight.

When planes fly supersonic, they make a very loud sound called a sonic boom. This boom is so loud that supersonic flight over land has been banned in the US since 1973. The X-59 is different. It is designed to make only a small, quiet sound like a car door closing.

The X-59 has flown 14 times already, but only at normal speeds. Now it is ready for its first supersonic flight. After that, it will try to fly at Mach 1.4, which is about 925 miles per hour. If it works, quiet supersonic passenger planes may fly over cities in the future.

supersonic

faster than the speed of sound, which is about 767 miles per hour (1,235 km/h) at sea level

sonic boom

a very loud explosive sound produced when an aircraft flies faster than the speed of sound

banned

officially not allowed by law or rule

Mach

a unit used to measure speed relative to the speed of sound; Mach 1 is exactly the speed of sound, Mach 2 is twice that speed

NASA

the National Aeronautics and Space Administration; the US government agency responsible for aviation and space exploration

experimental

designed to test new ideas or technology; an experimental aircraft is built to try out new ways of flying rather than to carry passengers

thump

a dull, quiet knocking sound; in this context, the much quieter noise the X-59 makes instead of a traditional sonic boom

milestone

an important event or achievement that marks progress toward a larger goal

Level 2 - Elementary

NASA's experimental X-59 aircraft is preparing for its first ever supersonic flight in early June 2026. The aircraft is part of the Quesst mission -- NASA's program to test quiet supersonic technology. The X-59 made its first flight at all on October 28, 2025, and has since completed 14 subsonic test flights, reaching speeds up to Mach 0.95, which is just below the speed of sound.

The sonic boom produced by supersonic aircraft has been one of the main reasons commercial supersonic flight over land is not allowed in the United States, a rule in place since 1973. The Concorde, the famous supersonic passenger jet that flew between 1976 and 2003, produced a boom of about 105 to 110 decibels -- roughly as loud as standing near a jet engine. The X-59 is designed to reduce that to just 75 decibels, approximately the sound of a car door closing.

In the upcoming supersonic tests, the X-59 will first cross Mach 1 at about 43,000 feet altitude. Later it will attempt to reach Mach 1.4 (925 mph) at 55,000 feet -- the flight conditions needed for the mission's second phase, when NASA will fly the aircraft over US cities and survey residents about what they hear. The data will be shared with aviation regulators to determine whether the law against supersonic overland flight should be updated.

subsonic

flying at speeds below the speed of sound, less than Mach 1

decibel

a unit used to measure the loudness of a sound; the higher the number, the louder the sound

altitude

the height of an object above sea level, usually measured in feet or meters

regulator

a government body or agency that makes and enforces rules for an industry, such as aviation or energy

phase

a distinct stage in a process or project, with its own goals and activities

survey

to ask a large group of people questions about their experiences or opinions in order to gather data

overland

over land rather than water; overland supersonic flight creates noise problems for communities below

aviation

the science and practice of flying aircraft; the aviation industry includes airlines, airports, and aircraft manufacturers

Level 3 - Intermediate

NASA's X-59, the centerpiece of the Quesst mission, is poised for its first supersonic flight within days. The aircraft, developed by Lockheed Martin's Skunk Works division, has accumulated 14 subsonic flights, with the most recent series reaching Mach 0.95 at 20,000 feet. The upcoming supersonic campaign will initially target Mach 1 at approximately 43,000 feet, then push toward the mission profile altitude of 55,000 feet at Mach 1.4 -- conditions specifically chosen to produce the aircraft's characteristic low-boom signature at the ground level.

The X-59 is 99.7 feet long with a 29.5-foot wingspan and is powered by a single General Electric F414 engine, the same engine that propels the Boeing F/A-18E/F Super Hornet. Its extreme length-to-width ratio is the key to its quiet performance. By extending the shockwave formation zone along the entire length of the fuselage, the aircraft prevents the multiple shockwaves that normally merge into a single loud boom. Instead, they reach the ground as a series of small pressure waves, perceived as a soft thump measured at approximately 75 Effective Perceived Noise decibels (EPNdB), compared to the Concorde's 105-110 EPNdB.

The Quesst mission follows a two-phase structure. Phase 1, concluding with the supersonic flights in June, validates the aircraft's technical performance and confirms that the low-boom shaping actually delivers the predicted noise reduction. Phase 2, scheduled for later in 2026, will see the X-59 fly over six or more US communities while NASA surveys public reaction to the thump versus the traditional boom. The community response data will be presented to the Federal Aviation Administration and the International Civil Aviation Organization as evidence for potentially revising the 1973 ban on civil supersonic flight over land.

shockwave

a cone-shaped pressure wave that forms ahead of and around an aircraft flying faster than sound; multiple shockwaves merging produce the classic sonic boom

fuselage

the main body of an aircraft, excluding the wings and tail; on the X-59 it is unusually long and thin

mission profile

the specific combination of speed, altitude, and flight path that an aircraft is designed to operate at for its intended mission

EPNdB

Effective Perceived Noise decibels; a unit that measures aircraft noise as it is actually perceived by human hearing, accounting for tone and duration

Federal Aviation Administration

the US government agency responsible for regulating civil aviation, including airspace rules, airline safety, and aircraft certification

length-to-width ratio

the relationship between an aircraft's length and its width; the X-59's extreme ratio is the key engineering feature enabling its low boom

campaign

a planned series of flight tests conducted over a period of time, each building on the results of the last

Level 4 - Advanced

NASA's X-59 Quesst stands at the threshold of its first supersonic flight, a technical watershed that has been decades in the conceptual making and five years in active development. The aerodynamic principle underlying its low-boom design -- sometimes called inverse-boom shaping -- exploits the slender body ratio and forward-swept canard alignment to distribute the aircraft's lift-induced pressure field over such an elongated spatial window that the individual shockwaves never reach coalescence before propagating to the ground. What the ear perceives as a thunderclap from a conventional supersonic aircraft is instead rendered as a sequence of low-amplitude pressure pulses, measured at approximately 75 EPNdB -- commensurate with a car door at 20 meters.

The regulatory rationale for the Quesst mission is grounded in the asymmetry between the 1973 FAA ban and the subsequent half-century of aeroacoustic research. The ban was promulgated in response to the Concorde's 105-110 EPNdB overland boom profile, a noise level that independent community studies demonstrated was both annoying and economically disruptive to properties on the flightpath. No aircraft since has had the technical capability to challenge that regulatory baseline -- until the X-59. The Phase 2 community overflight surveys, planned for a subset of US cities with demographically diverse noise-tolerance profiles, are specifically designed to generate an ICAO-standard noise exposure dataset that cannot be dismissed as modeling artifacts.

The commercial implications of a favorable regulatory revision extend well beyond NASA. Boom Supersonic's Overture, United Airlines' prospective fleet buy of 15 aircraft, and a cluster of clean-sheet supersonic business jet programs (Aerion was the pioneer before its 2021 liquidation) are all commercially stranded pending a revision of FAA FAR Part 91.817, the operative rule. A successful X-59 flight campaign followed by a Phase 2 community acceptance threshold would provide the evidentiary basis for a Notice of Proposed Rulemaking that the FAA has, until now, had no scientific justification to issue. The X-59 is thus not only a flight test aircraft but the key that unlocks an estimated $100 billion addressable market in civil supersonic transport.

coalescence

the merging of separate elements into a single unified whole; in aeroacoustics, the coalescence of multiple shockwaves produces the characteristic loud sonic boom

aeroacoustics

the branch of fluid mechanics that studies the generation and propagation of sound by moving fluids, especially the noise produced by aircraft

promulgated

formally issued or announced by an authority with the force of law or official rule

ICAO

International Civil Aviation Organization; the UN specialized agency that sets international standards for aviation safety, security, and environmental performance

Notice of Proposed Rulemaking