NASA’s X-59 quiet supersonic aircraft achieved a significant milestone in March 2025, successfully completing its engine speed hold test at Armstrong Flight Research Center on Edwards Air Force Base. This “cruise control” feature, tested on the ground, ensures the aircraft can maintain precise speeds during flight, bringing it closer to its anticipated first flight later this year.
Paul Dees, NASA’s X-59 deputy propulsion lead, described the system’s role. “Engine speed hold is essentially the aircraft’s version of cruise control,” he said. “The pilot engages speed hold at their current speed, then can adjust it incrementally up or down as needed.” Unlike a prior test of the engine in isolation, this March trial verified the function within the X-59’s fully integrated avionics.
“We needed to verify that speed hold worked not just within the engine itself but as part of the entire aircraft system,” Dees explained. “This test confirmed that all components—software, mechanical linkages, and control laws—work together as intended.” The X-59, a joint effort with Lockheed Martin, aims to soften sonic booms into a quiet thump, potentially revolutionizing supersonic travel.
The test boosts safety for the upcoming first flight. “The pilot is going to be very busy during first flight, ensuring the aircraft is stable and controllable,” Dees said. “Having speed hold offload some of that workload makes first flight that much safer.” At speeds exceeding Mach 1 (approximately 767 mph at sea level), this precision reduces pilot burden, allowing focus on stability and data collection.
Initially planned for later aluminum bird tests—simulations of normal and failure scenarios—the team capitalized on an earlier chance. “It was a target of opportunity,” Dees noted. “We realized we were ready to test engine speed hold separately while other systems continued with finalizing their software. If we can learn something earlier, that’s always better.” This efficiency accelerates the project timeline.
The X-59, part of NASA’s Quesst mission, is designed to cruise at 925 mph with minimal noise, a feat that could lift the U.S. ban on overland supersonic flight, in place since 1973, per NASA’s website. Built by Lockheed Martin’s Skunk Works in Palmdale, California, the 94-foot aircraft uses a General Electric F414 engine. Its testing at Edwards marks steady progress toward aviation history.
Each successful test narrows the gap to the X-59’s debut. Data from its first flight will inform regulators, potentially reshaping commercial air travel. As the team prepares for takeoff, the quiet supersonic era draws nearer, promising faster, less disruptive journeys.
