A so-called 'successor to Concorde' capable of flying from London to New York in under four hours is edging ever closer to its first flight.

The aircraft is anticipated to reach Mach 1.5, approximately 990 mph (1,590 kph), meaning it could potentially complete a nonstop transatlantic crossing from the UK capital to the Big Apple in roughly three hours and 44 minutes.

Concorde boasted a maximum cruising speed of Mach 2.04, or 1,354 mph (2,179 kph), more than twice the speed of sound, which allowed it to touch down in New York City in approximately three hours.

Conventional commercial flights typically take around seven to eight hours to complete the same journey.

The X-59 has been engineered to travel at supersonic speeds while generating a quiet thump rather than a thunderous sonic boom — a noise problem that has long rendered such aircraft unfit for flight over densely populated areas.

The plane is currently being put through its paces at the U.S. Air Force Plant 42 in Palmdale, California, where safety systems are presently being assessed.

Its debut flight will feature a lower-altitude loop at around 240 mph to confirm system integration, marking the beginning of a flight-testing phase focused on establishing the aircraft's airworthiness and overall safety credentials.

During subsequent test flights, the X-59 will climb to greater altitudes and increase velocity, eventually breaking the sound barrier.

NASA Armstrong declared on Friday (Sep 12):

"As NASA's one-of-a-kind X-59 quiet supersonic research aircraft approaches first flight, its team is mapping every step from taxi and takeoff to cruising and landing - and their decision-making is guided by safety."