NASA's X-59 'quiet' supersonic jet aces key 'cruise control' test ahead of 1st flight

NASA's new X-59 supersonic jet sits on the runway at Lockheed Martin Skunkworks in Palmdale, California. .

NASA's new X-59 supersonic jet is a step closer to flight after passing an important ground test in March.

Known as "engine speed hold," the test ensured that the X-59 can maintain a specific speed when it flies for the first time later this year.