NASA’s strange-looking X-59 jet is about to reach the milestone it was built for: flying faster than the speed of sound.
NASA’s X-59 experimental aircraft is preparing for one of the most important phases of its flight testing program. The next series of flights will include the aircraft’s first journey beyond the speed of sound, along with several key tests needed for the mission’s future goals.
“What comes next is the first time this one-of-a-kind aircraft will fly supersonic,” said Cathy Bahm, project manager for NASA’s Low Boom Flight Demonstrator. “We are starting toward the mission conditions test point that X-59 was designed for.”
Following months of flight testing, the X-59 team completed a review of recent progress in late May and is now moving on to a new set of tests involving greater speeds and higher altitudes. These flights will help engineers evaluate how the aircraft performs under the operating conditions required for NASA’s Quesst mission, which aims to collect data on quiet supersonic flight.
First Supersonic Flights Ahead
NASA expects the X-59 to exceed the speed of sound for the first time during test flights scheduled for early June. The aircraft is expected to fly faster than 630 mph at an altitude of about 43,000 feet, marking a major achievement for the program.
The aircraft will then attempt a “mission conditions” flight, reaching Mach 1.4 (925 mph) at roughly 55,000 feet. Those targets are especially important because they match the performance conditions NASA plans to use when flying the X-59 over U.S. communities in future tests. During those flights, researchers hope to gather public feedback on the aircraft’s quieter sonic “thump.”
Although the X-59 was specifically designed to reduce the disruptive sonic boom normally associated with supersonic flight, the upcoming tests are not intended to demonstrate that capability. During this phase, the aircraft will fly alongside a conventional supersonic chase plane. Any quiet sound produced by the X-59 will be masked by the louder sonic booms generated by the chase aircraft.
Later this summer, the chase plane will carry a specialized shock-sensing probe that will allow researchers to begin measuring the X-59’s shock waves.
Milestones From Earlier Test Flights
The aircraft’s first phase of flight testing successfully achieved a number of objectives and provided engineers with valuable data.
After its maiden flight in October 2025, the X-59 underwent a planned maintenance period before returning to flight operations in March 2026. Since then, the aircraft has completed 14 additional flights and reached several important milestones, including:
- Performing its first gear swing, retracting its landing gear in flight and revealing its distinctive streamlined shape.
- Flying as high as 43,000 feet and reaching near-supersonic speeds of Mach 0.95, approximately 627 mph.
- Completing its first day with two flights, a pace that later became increasingly routine as testing accelerated.
- Transitioning from higher-speed and higher-altitude operations to slower and lower-altitude testing to study the aircraft’s behavior across a wider range of conditions.
Engineers used data from these flights to evaluate critical systems, including fuel delivery, hydraulics, environmental controls, and the aircraft’s eXternal Vision System. Instead of a traditional forward windshield, the X-59 relies on cameras that feed images to a display, allowing the pilot to see ahead.
Teams also closely monitored the aircraft during takeoffs, landings, and flight operations. Strain gauges installed throughout the airframe measured structural loads and recorded how the aircraft responded to those forces.
Expanding the Flight Envelope
During the upcoming test campaign, pilots will continue working through planned test points while engineers monitor how the aircraft performs under supersonic conditions.
“Flying at supersonic speeds is a major milestone for the X-59 team,” Bahm said. “Every step of envelope expansion brings us closer to demonstrating the quiet supersonic capability that is at the heart of the Quesst mission. Completing the first mission-conditions flight is especially meaningful – it’s the moment where we begin validating the aircraft in the environment it was designed for.”
In addition to reaching mission conditions, the X-59 is expected to achieve its top planned performance targets of Mach 1.6 (1,218 mph) and an altitude of 60,000 feet.
Even so, not every future flight will be supersonic. The testing program will continue to include slower flights and operations at lower altitudes so engineers can evaluate the aircraft under a broad range of conditions.
“These flights not only deepen our confidence in the X-59’s performance – they mark our progression toward the future phases of the mission that will ultimately help shape the future of supersonic travel,” Bahm said.
Preparing for Quesst Phase 2
All flights completed so far, as well as those planned in the upcoming series, are part of Phase 1 of NASA’s Quesst mission. The goal of this stage is to verify the aircraft’s performance and airworthiness.
Some of these flights will also begin testing equipment needed for future research, including a probe mounted on one of NASA’s F-15 research aircraft to measure the unique shock-wave signature produced by the X-59.
Information gathered during those early measurements will help prepare the team for Quesst Phase 2, scheduled to begin later this year. During that phase, engineers will directly measure the aircraft’s supersonic flight signature to confirm that it produces the quiet supersonic thump it was designed to create.
“Aviation pioneer Otto Lilienthal said, ‘To design a flying machine is nothing. To build one is something. But to fly is everything.’ The 15 X-59 flights we’ve accomplished since March have been everything to this team and the mission,” Bahm said. “Every flight has pushed the boundaries of what’s possible, steadily expanding the envelope and strengthening our confidence in the aircraft.”
While the accomplishments so far have been significant, Bahm said the team remains focused on what comes next.
“As we look ahead to the upcoming flights, we’re poised to open the envelope even further – moving boldly toward the mission test point this aircraft was built to achieve,” Bahm said. “Flying supersonic and reaching these milestones isn’t just progress; it’s the realization of years of perseverance, innovation, and teamwork. Each step brings us closer to Phase 2, and to the future of commercial supersonic flight.”
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1 Comment
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