NASA has started production of a plane that will fly faster than the speed of sound, but will be almost inaudible from the ground below.

The US space agency plans to bring supersonic speeds back to commercial air travel with the X-Plane. But unlike its predecessor Concorde, its sonic booms will be too soft to be noticed from the ground.

If all goes to plan, the piloted aircraft will be built and delivered to NASA’s Armstrong Flight Research Centre by the end of 2021, and will be approved for commercial use by 2025.

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