The breakthrough could nearly halve future commercial journeys over the Atlantic from seven hours to four
Nasa's spiritual successor to the Concorde has successfully surpassed the speed of sound without generating a thunderous sonic boom, long preventing supersonic travel over populated areas.
The experimental X-59 aircraft, nicknamed the "Son of Concorde", forms the core of the space agency's Quesst mission and reached Mach 1.4 (924mph) during its test flight from Edwards Air Force Base in California.
Flying at an altitude of 55,000 feet, the sleek jet measuring just under 100 feet in length produced merely a soft "sonic thump", rather than the ear-splitting crack typically associated with breaking the sound barrier.
This achievement marks a landmark step towards restoring supersonic aviation over civilian-occupied zones, which could greatly reduce travel time for such aircraft.
The aircraft's distinctive design enables the noise reduction, with a needle-shaped nose comprising roughly one-third of the plane's total length.
This aerodynamic front section gradually parts the air, preventing shockwaves from combining into a single explosive boom.
Additionally, engineers positioned the engine atop the fuselage, directing remaining sound waves upward and away from the ground below.
Larry Cliatt, a Nasa aerospace engineer leading testing for the Quesst mission's later phases, described the breakthrough as "a huge deal for us".
Mr Cliatt said the newly achieved sound should resemble "a car door closing across a car park", rather than an explosion.
The United States prohibited commercial aircraft from exceeding the speed of sound over its territory in 1973, following widespread complaints from residents during sonic boom testing above Oklahoma City.
This restriction meant the Anglo-French supersonic airliner Concorde – which operated at twice the speed of sound until its retirement in 2003 – could only achieve its maximum velocity over the Atlantic Ocean.
President Donald Trump has now signed an executive order aimed at overturning this decades-old regulation.
He said: "For more than 50 years, outdated and overly restrictive regulations have grounded the promise of supersonic flight over land, stifling American ingenuity and ceding leadership to foreign adversaries."
Nasa anticipates the X-59 will produce sound levels of near 75 perceived loudness decibels, compared with over 100 for Concorde – a difference the agency believes could transform aviation.
Should future aircraft match the X-59's capabilities, transatlantic journeys from Washington DC to London could take roughly four hours, instead of the current seven.
Flights between New York and Los Angeles might be completed in under three hours, halving present travel times.
Built jointly by Nasa and Lockheed Martin, the single-seat X-59 is not designed as a template for passenger jets but will instead gather crucial data to inform the development of commercial supersonic aircraft for future implementation.