Supersonic 'Son of Concorde' jet that could fly London to NYC in under 4 hours smashes key speed test

A supersonic that could slash flight times in half has reached record speeds in its latest test flight.

was performing the seventh of its ten subsonic test flights on Tuesday when it hit the new top speed. Engineers are in the process of tinkering with the impressive aircraft, nicknamed the 'son of ', to make it supersonic.

It reached a rapid Mach 0.81, dwarfing the Mach 0.67 it achieved on the flight before, with the also reaching a new maximum altitude of 23,015ft. This was 3,000ft more than the previous test.

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Boom wrote in its test flight update: "XB-1 reached a new top altitude of 23,015 feet, allowing the team to perform a final cockpit pressurization test at maximum pressure differential, ensuring that it is safe to proceed up to 30,000 feet – the altitude XB-1 will fly when it reaches ."

The engineers have the task of pushing the aircraft until it reaches the speed of sound, Mach 1. From take-off to landing, the flight - which was piloted by Tristan “Geppetto” Brandenburg - lasted around 55 minutes.

Boom has not yet revealed the date of flight number eight, but it could happen in as little as two weeks' time. The company performed test flights inside a similar timeframe in September and October.

The aviation firm is one of many competing to build the successor to the British supersonic jet, which is known in the industry as the "Son of Concorde". The aircrafts were banned in the UK in 2003 due to the supersonic boom it created, and due to how expensive it was to operate - which made it inaccessible for most customers.

The UK's aerospace watchdog has said it will review the ban after several manufacturers, including NASA and Lockheed Martin, announced they are developing new models.