XB-1 Flight Test Program Live Blog
XB-1, Boom’s supersonic demonstrator aircraft, successfully broke the sound barrier three times during its first supersonic flight on January 28, 2025. Beginning with XB-1’s historic first flight on March 22, 2024, the aircraft steadily progressed through a series of test flights at increasing speeds as it approached and ultimately exceeded Mach 1 – becoming the first civil supersonic jet to do so since Concorde. XB-1 is the world’s first independently developed supersonic jet, and the first civil supersonic jet designed and built in America.
XB-1 provides the foundation for the design and development of Overture, Boom’s supersonic airliner. XB-1 leverages state-of-the-art technologies to enable efficient supersonic flight including digitally-optimized aerodynamics, carbon fiber composites, advanced supersonic engine intakes, and an augmented reality vision system for takeoff and landing visibility.
XB-1’s Road to Supersonic: By the Numbers
The XB-1 team brings over one thousand years of combined aerospace experience and has devoted nearly two years to ground and flight testing XB-1 in Mojave, CA—all driven by one mission: supersonic flight.
From thousands of hours reviewing ground and flight test data, to more than a few games of pre-flight pickleball, every number tells the story of how far the team has come on the journey to making supersonic a reality. The team accomplished the goal of safely breaking the sound barrier – not just once, but three times – during XB-1’s first supersonic flight on January 28, 2025.
Here, we are sharing updates on each of XB-1’s test flights, documenting its progression up to the sound barrier and beyond.
Feb 10, 2025 – XB-1 Flight 13: Second Supersonic Flight
Jan 28, 2025 – XB-1 Flight 12: First Supersonic Flight
Feb 10, 2025
XB-1 Flight 13: Second Supersonic Flight
Max altitude: 36,514 feet
Speed: Mach 1.18 (671 KTAS, or 772 mph)
Flight time: approximately 41 minutes
Pilot: Chief Test Pilot Tristan “Geppetto” Brandenburg
Key test points:
- Continue flying and handling qualities assessments at supersonic speeds
- Capture specialized photography and sonic boom data
- Expand Mach number to 1.14 or above
On February 10, 2025, XB-1 once again flew faster than the speed of sound, collecting key data on civil supersonic flight. Following its historic first supersonic flight on January 28, 2025, the XB-1 team moved quickly into planning for the second supersonic flight, the thirteenth flight in its groundbreaking flight test program.
The mission of XB-1’s second supersonic flight was to continue to assess aircraft performance and data collection above Mach 1, including capturing acoustic sonic boom data and specialized photography known as Schlieren images.
Schlieren images provide a way to visualize the shock waves resulting from XB-1 pushing through the air at supersonic speeds. Taking Schlieren images requires ideal conditions and timing. Boom Chief Test Pilot Tristan “Geppetto” Brandenburg positioned XB-1 at an exact time in a precise location over the Mojave Desert to enable a team on the ground to photograph XB-1 in-flight. The images document the changing air density around the aircraft at supersonic speeds, showing the resulting shock wave—making the invisible visible.
Boom continued to gather essential data for supersonic commercial flight, including capturing acoustic sonic boom data with microphones and sound pressure level recording devices positioned in strategic locations in relation to the flight path. This type of data from XB-1’s first supersonic flight demonstrated that supersonic flight without the disturbance of a sonic boom is possible—opening the door to quiet supersonic travel over land onboard Overture, with Boomless Cruise. Boomless Cruise is based on well-established physics known as Mach cutoff, in which a sonic boom refracts in the atmosphere and never reaches the ground. This effect is achieved by breaking the sound barrier at a high enough altitude, with exact speeds varying based on atmospheric conditions.
Teams on the ground confirmed once again that XB-1 broke the sound barrier three times during this flight without an audible sonic boom reaching the ground.
XB-1’s second supersonic flight also marks the conclusion of its groundbreaking flight test program. Following this final flight, XB-1 will return to its birthplace in Denver, Colorado. Boom will now focus its full efforts on scaling XB-1 learnings and technology to build the Overture supersonic airliner.
Watch a replay of the livestream for this flight, hosted by Founder and CEO Blake Scholl and Chief Flight Test Engineer Nick Sheryka here.
Jan 28, 2025
XB-1 Flight 12: First Supersonic Flight
Max altitude: 35,290 ft
Speed: Mach 1.122 (652 KTAS or 750 mph)
Flight time: approximately 34 minutes
Pilot: Chief Test Pilot Tristan “Geppetto” Brandenburg
Key test points:
- Safely break the sound barrier
- Expand Mach number to 1.1 or above
- Measure flying and handling qualities and flutter margin at supersonic speed
The successful first supersonic flight of Boom’s demonstrator aircraft, XB-1, took place on January 28, 2025 at the Mojave Air & Space Port in California. Boom designed, built, and flew the world’s first independently developed supersonic jet—the first civil supersonic jet made in America.
Flown by Boom Chief Test Pilot Tristan “Geppetto” Brandenburg, XB-1 entered the Bell X-1 Supersonic Corridor and reached an altitude of 35,290 feet before accelerating to a top speed of Mach 1.122 (652 KTAS or 750 mph) over the course of not one, not two, but three supersonic runs—breaking the sound barrier three times on its historic first supersonic flight.
Watch a replay of the livestream, hosted by Former Chief Concorde Pilot for British Airways Mike Bannister, Boom Chief Flight Test Engineer Nick Sheryka and Boom advisor and former Chief Engineer Greg Krauland. The broadcast includes air-to-air capture of the moment XB-1 exceeded Mach 1 for the first time, enabled by a Starlink unit in one of two chase planes. You can also catch a Q&A session with Bannister, Geppetto, and Boom founder and CEO, Blake Scholl.
XB-1’s first supersonic flight took place in the same historic airspace where Chuck Yeager broke the sound barrier for the first time in 1947, among many other historic firsts. The first supersonic flight of XB-1 marks the first human-piloted civil supersonic flight since Concorde’s retirement over 20 years ago, paving the way for the return of commercial supersonic flight onboard Overture.
Jan 10, 2025
XB-1 Flight 11
Max altitude: 29,481 ft
Speed: Mach 0.95 (575 knots true airspeed)
Flight time: approximately 44 minutes
Pilot: Chief Test Pilot Tristan “Geppetto” Brandenburg
Key test points:
- Expanding dynamic pressure to 383 KEAS
- Testing XB-1 at higher dynamic pressure than it will experience at supersonic speeds
- Final handling checks ahead of supersonic flight
XB-1 started the new year with a successful Flight 11 on January 10, 2025 as it closes in on supersonic flight. In 2024, XB-1 completed 10 test flights at the Mojave Air & Space Port in Mojave, CA.
During the 44-minute flight, Boom Chief Test Pilot Tristan “Geppetto” Brandenburg took XB-1 to an altitude of 29,481 feet. Flight 11 again reached a transonic top speed of Mach 0.95, faster than the cruising speed of today’s airliners. An aircraft flies transonic when it reaches the range of speeds just below supersonic, which is Mach 1.
The primary objective for Flight 11 was expanding dynamic pressure to 383 KEAS (knots equivalent airspeed)—a higher number than will be experienced during XB-1’s first supersonic flight. This is the highest dynamic pressure the aircraft will ever experience—pushing beyond the anticipated pressure the aircraft will experience at Mach 1.1.
As an aircraft approaches supersonic speeds, dynamic pressure becomes a key factor—it’s essentially how hard the plane is pushing through the air. Dynamic pressure and Mach number work together to shape the aircraft’s performance. During flight testing, we carefully expand one parameter at a time—either Mach number or dynamic pressure—in order to ensure safe and precise performance. The relationship between these two numbers changes with altitude—the faster and lower you are, the higher the dynamic pressure, and vice versa.
Following a thorough data review of aircraft performance and handling qualities on Flight 11, the team will determine whether another test flight is needed prior to taking XB-1 to supersonic speeds. XB-1 is on track to break the sound barrier in early 2025.
Dec 19, 2024
XB-1 Flight 10
Max altitude: 32,417 ft
Speed: Mach 0.95 (553 knots true airspeed)
Flight time: approximately 46 minutes
Pilot: Chief Test Pilot Tristan “Geppetto” Brandenburg
Key test points:
- New max speed and altitude
- Pushing further into the transonic range
- Clearing additional flutter test points before supersonic
- Confirming safe operation at Mach 0.9 with the stability augmentation system off
On December 19, 2024, XB-1 successfully completed its 10th test flight, reaching a new top speed of Mach 0.95 and pushing further into the transonic regime – the speed range just below supersonic. An aircraft enters the transonic regime when flying between approximately Mach 0.8 and Mach 1.2.
During the approximately 46-minute flight piloted by Chief Test Pilot Tristan “Geppetto” Brandenburg, XB-1 reached a new maximum altitude of 32,417 feet and a new top speed of Mach 0.95 (553 knots true airspeed). At XB-1’s new top speed, it flew faster than the cruising speed of a Boeing 787 or Airbus A380, which is about Mach 0.85. XB-1’s new top altitude positions the aircraft near the altitude at which it will fly supersonic speeds, which is approximately 34,000 feet.
The XB-1 team assessed aircraft handling qualities at Mach 0.9 with the stability augmentation system off. XB-1 cleared this requirement, confirming that the pilot can safely control the aircraft at higher speeds even in the unlikely event of a stability augmentation system failure.
The team tested critical flutter points at Mach 0.85, 0.9, and 0.95 at varying altitudes to ensure the aircraft structure continues to behave as predicted in the expanded flight envelope. This type of testing measures the interaction of the aircraft structure with the atmosphere it is flying through. The remaining subsonic flight tests will focus on expanding dynamic pressure to a higher number than will be experienced during XB-1’s first supersonic flight.
Completing two successful test flights within a week, XB-1 is steadily progressing toward breaking the sound barrier in early 2025. We anticipate 1-2 additional flights to complete final system checks before XB-1’s supersonic flight.
Dec 13, 2024
XB-1 Flight 9
Max altitude: 27,716 ft
Speed: Mach 0.87 (517 knots true airspeed)
Flight time: approximately 56 minutes
Pilot: Chief Test Pilot Tristan “Geppetto” Brandenburg
Key test points:
- New max speed and altitude
- Clearing new flutter test point at Mach 0.85
- Durability testing of new drag-reducing material applied to underbelly
On December 13, 2024, XB-1 successfully completed its ninth test flight, reaching a new top speed of Mach 0.87 (517 knots true airspeed) and clearing critical system checks as it approaches supersonic flight. XB-1 reached a new maximum altitude of 27,716 feet.
Flight nine focused on clearing flutter points at increased speeds and varying altitudes to ensure the aircraft structure continues to behave as predicted in the expanded flight envelope. This type of testing measures the interaction of the aircraft structure with the atmosphere it is flying through and is critical as XB-1 continues to reach higher speeds.
This flight successfully demonstrated updates to the flutter excitation system (FES). During XB-1’s previous test flight on November 16, the team gathered key insights about the flutter testing equipment and incorporated improvements into the design of the FES. The team diligently refined tools and processes—many of which need to be created from scratch for the unique needs of XB-1—to ensure the safe and effective envelope expansion of the first independently developed supersonic jet.
These modifications enable a safer and more efficient progression through the transonic and supersonic regimes in the remaining test flights. We anticipate an additional flight to accomplish all safety checks prior to supersonic flight, which we are now targeting in early 2025.
We also continued a series of tests in collaboration with the Defense Innovation Unit (DIU) and Air Force Operational Energy Office. Before flight eight, the team applied a shark skin-inspired ‘riblet’ package to XB-1’s aft underbelly for durability testing at transonic and supersonic speeds. The XB-1 new material, made by MicroTau, aims to reduce drag, fuel consumption, and emissions, especially at high speeds.
Nov 16, 2024
XB-1 Flight 8
Max altitude: 25,040 ft
Speed: Mach 0.82 (487 knots true airspeed)
Flight time: approximately 54 minutes
Pilot: Chief Test Pilot Tristan “Geppetto” Brandenburg
Key test points:
- Confirming safe operation at Mach 0.8 with the stability augmentation system off
- Expanding the altitude envelope to over 25,000 feet
On November 16, 2024, XB-1 successfully completed its eighth of ten planned subsonic test flights as the demonstrator aircraft closes in on supersonic flight before year-end.
Flight eight assessed aircraft handling qualities with the stability augmentation system off. XB-1 cleared this requirement, confirming that the pilot can safely control the aircraft at higher speeds even in the event of a stability augmentation system failure.
Designing a plane that is both very stable and very fast is a challenge, especially for high-speed aircraft like XB-1. One of the major accomplishments of the XB-1 program was converging on a design that does not rely on computerized augmentation to stay safe in the air, unlike many modern fighter jets that use automated systems to make constant adjustments to the flight path in order to maintain stability. While XB-1 does have this kind of system, called the stability augmentation system, the team is assessing the aircraft with the system off at increasing speeds—this is a requirement prior to supersonic flight that XB-1 successfully cleared during this flight.
We also introduced a new series of tests in collaboration with the Defense Innovation Unit (DIU) and Air Force Operational Energy Office. We’re testing the durability of a new material by MicroTau—a shark skin-inspired ‘riblet’ package that aims to reduce drag, fuel consumption, and emissions, especially at high speeds. We applied the material to XB-1’s aft underbelly and will evaluate it at transonic and supersonic speeds.
Nov 5, 2024
XB-1 Flight 7
Max altitude: 23,015 ft
Speed: Mach 0.82 (499 knots true airspeed)
Flight time: approximately 55 minutes
Pilot: Chief Test Pilot Tristan “Geppetto” Brandenburg
Key test points:
- New top speed of Mach 0.82 (499 knots true airspeed)
- Expanded altitude envelope to 23,015 ft
- Cockpit pressurization test at maximum pressure differential
- FES testing at Mach 0.7, 0.75, and 0.8 test points
On November 5, 2024, XB-1 successfully completed its seventh of ten planned subsonic test flights as the team continues to make steady progress toward supersonic flight. Flight seven focused on flutter envelope expansion and cockpit pressure testing in order to ensure safe performance and handling qualities as XB-1 approaches supersonic speeds and higher altitudes.
This flight marks a new top speed for XB-1 at Mach 0.82, or 499 knots true airspeed. The XB-1 team performed tests of the flutter excitation system (FES) at higher speeds than previous flights – hitting Mach 0.7, 0.75, and 0.8 test points to ensure that the aircraft handles predictably up to transonic speeds.
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 supersonic speeds. This is a human-piloted aircraft, so just like the pressurized cabin in every airliner, XB-1 maintains a pressurized environment for the pilot due to the physiological issues that occur at high altitude.
XB-1 continues to perform at progressively faster speeds and higher altitudes, expanding the flight envelope gradually to prepare the aircraft and team for breaking the sound barrier at Mach 1.
Oct 25, 2024
XB-1 Flight 6
Max altitude: 20,000 ft
Speed: Mach 0.67
Flight time: approximately 38 minutes 30 seconds
Pilot: Chief Test Pilot Tristan “Geppetto” Brandenburg
Key test points:
- Demonstrated successful flutter test point at increased airspeed at 0.65 Mach
- Demonstrated successful FES operation in flight
- Expanded altitude envelope to 20,000 ft
On October 25, 2024, XB-1 successfully completed its sixth test flight and continues to make progress in expanding the envelope for supersonic flight.
Flight six primarily targeted flutter and handling qualities testing at a higher altitude than previous flights. The FES, or flutter excitation system, is crucial in testing new aircraft to ensure there are no undesirable interactions between the airflow around the vehicle and the structure of the aircraft. Flutter is a phenomenon where the energy from the airflow can interact with the airframe vibration modes and cause structural failure. Modern aircraft design uses tools and predictions to develop aircraft that should not be susceptible to flutter, which we verify with testing. In this flight, XB-1 made significant progress towards validating a fully functional FES system.
Unfortunately, we did experience a degradation in GPS signal strength which impacted our ability to accomplish more in this flight. The team is currently troubleshooting this issue and as soon as the source of interference is identified and corrected, we will be on to Flight 7.
Boom’s Flight Test Program Approach
Nick Sheryka, XB-1 Chief Flight Test Engineer, speaks to Boom’s progressive approach to flight testing, which is rooted in our philosophy that safety is the ultimate mission.
Oct 7, 2024
XB-1 Flight 5
Max altitude: 17,800 ft
Speed: 0.69 (428 knots, TAS)
Flight time: approximately 50 minutes
Pilot: Chief Test Pilot Tristan “Geppetto” Brandenburg
Key test points:
- New top speed of Mach 0.69 (428 knots, TAS) achieved
- Landing gear up right after takeoff
- Continued testing of the flutter excitation system (FES) at Mach 0.6
- Handling quality, flutter, and pacer checks at progressively higher speeds
On October 7, 2024, XB-1 took to the skies for its fifth flight from the Mojave Air & Space Port, climbing to 17,800 feet in the R-2515 Airspace. Flown by Chief Test Pilot Tristan “Geppetto” Brandenburg, XB-1’s fifth successful flight marks the halfway point of the 10 planned subsonic test flights before breaking the sound barrier. This is the fastest, highest, and longest flight so far as XB-1 progresses through the flight test program on the way to supersonic flight later this year.
The flutter excitation system (FES) was repaired and reinstalled for this flight in order to continue data collection at the Mach 0.6 flutter point. The FES is a critical system during this phase of test flights, and will be used extensively to clear the flight envelope up to transonic speeds. Flying and handling quality checks were performed at progressively higher speeds, including pacer checks and flutter tests as XB-1 reached a new top speed at Mach 0.69 (or 428 knots, true airspeed). The landing gear was retracted immediately following takeoff, which will become standard procedure during future test flights.
What Happens Between Flights?
XB-1 Senior Manager of Aircraft Systems Erin Young shares what happens inside the test, analyze, and review process between test flights as the aircraft continues to progress toward Mach 1.
Sep 21, 2024
XB-1 Flight 4
Max altitude: 16,150 ft
Speed: 0.617 (382 knots, TAS)
Flight time: approximately 48 minutes
Pilot: Chief Test Pilot Tristan “Geppetto” Brandenburg
Key test points:
- New top speed of Mach 0.617 achieved
- First use of the flutter excitation system (FES) in flight
- Handling quality checks between 225 and 300 knots
- Applied elevated g-forces of 2.78g in preparation for supersonic flight
- Landing gear extended and retracted at 225 knots (max safe speed)
Just eight days after its third test flight, XB-1 successfully completed its fourth – and fastest – test flight on September 21, 2024. During this flight, XB-1 reached the highest speeds so far at Mach 0.617, or 382 knots true airspeed – more than halfway to breaking the sound barrier at Mach 1.
This flight marks the first use of the flutter excitation system (FES) in flight. The FES is a vibration device that we can turn on in order to hit structural vibration modes deliberately before we would encounter them naturally in flight.
In addition to checking basic handling qualities of the aircraft at various speeds between 225 and 300 knots, the team took XB-1 up to 2.78g (or g-force), using a flight test technique called a wind up turn to put elevated g-forces on an aircraft. This is the highest we intend to see during XB-1’s flight test program. When we get to supersonic flight, XB-1 will have to clear a turn at 2g to line up for the supersonic run – the team is testing the aircraft with an extra margin to increase safety.
The landing gear was retracted at a max speed of 225 knots, completing this portion of system testing. During future test flights, the team will retract the landing gear immediately after takeoff.
The flight reached a maximum altitude of 16,150 feet, with a total flight time of 48 minutes. XB-1 was flown by Boom Chief Test Pilot, Tristan “Geppetto” Brandenburg, who flew the second and third flights of XB-1 and will also pilot the aircraft’s first supersonic flight.
Sep 13, 2024
XB-1 Flight 3
Max altitude: 15,000 ft
Speed: 289 knots, TAS
Flight time: approximately 32 minutes
Pilot: Chief Test Pilot Tristan “Geppetto” Brandenburg
Key test points:
- Achieved maximum pitch and yaw attitudes expected in flight
- Environmental control system (ECS) checks and tuning
- Landing gear extended and retracted at 215 knots
- Continued testing of the stability augmentation system
On September 13, 2024, XB-1 flew for the third time, and Chief Test Pilot Tristan “Geppetto” Brandenburg was at the controls.
During this flight, the team continued to test key systems and performance as they systematically expand the flight envelope. The pilot, Geppetto, took XB-1 to the maximum pitch and yaw attitudes that we expect to see in flight. This testing was done at a safe, higher altitude to ensure there were no unexpected handling qualities. We do this kind of testing so that the first time it happens, it is not in a critical phase of flight.
The team also checked the performance of the environmental control system (ECS), which controls the temperature and pressurization of the cockpit. This test is to ensure that the ECS is functioning as designed before XB-1 goes to higher altitudes, where it is colder and the pressure is lower. The landing gear was extended and retracted at higher speeds than previous flights (215 knots), marking the second of three steps working up to the maximum safe speed for raising and lowering the gear, which is 225 knots. Additionally, the team continued testing of the stability augmentation system.
Read more on XB-1’s third flight here.
Aug 26, 2024
XB-1 Flight 2
Max altitude: 10,400ft
Speed: 270 knots, TAS
Flight time: approximately 15 minutes
Pilot: Chief Test Pilot Tristan “Geppetto” Brandenburg’s first flight in XB-1
Key test points:
- Landing gear retracted and extended in-flight for the first time
- Digital stability augmentation system demonstrated in-flight
- Tufting applied to the right wing in order to verify aerodynamic characteristics
In August, XB-1 successfully completed its second flight at the Mojave Air & Space Port in Mojave, California with Chief Test Pilot Tristan “Geppetto” Brandenburg at the controls for the first time.
The landing gear was retracted and extended in flight for the first time, which is typical of second test flights. The XB-1 team also assessed aircraft handling qualities, and demonstrated a new stability augmentation system, or roll damper. This roll damper was implemented to improve handling qualities based on learnings from first flight.
Read more on XB-1’s second flight here.
Mar 22, 2024
XB-1 Successfully Completes First Flight
Max altitude: 7,120ft
Speed: 264 knots, TAS
Flight time: 12 minutes
Pilot: Bill “Doc” Shoemaker
Key test points:
- Initial assessment of the aircraft’s handling qualities
- Airspeed checks with the T-38 chase aircraft
- Assessing the aircraft’s stability in the landing attitude
On March 22, 2024, XB-1, the world’s first independently developed supersonic jet, took flight for the first time at the Mojave Air & Space Port in Mojave, California.
Piloted by Test Pilot Bill “Doc” Shoemaker, XB-1 safely and successfully achieved an altitude of 7,120 feet and speeds up to 238 knots (273 mph). While XB-1 was in the air, the team performed an initial assessment of the aircraft’s handling qualities, including airspeed checks with the T-38 chase aircraft, and assessing the aircraft’s stability in the landing attitude (at a high angle of attack).
“XB-1 took flight in the same hallowed airspace where the Bell X-1 first broke the sound barrier in 1947,” said Blake Scholl, founder and CEO of Boom Supersonic. “I’ve been looking forward to this flight since founding Boom in 2014, and it marks the most significant milestone yet on our path to bring supersonic travel to passengers worldwide.”
Two decades after Concorde’s retirement, the historic first flight of XB-1 marked the return of a civil supersonic aircraft to the skies and paves the way for the revival of mainstream supersonic travel onboard Overture, Boom’s sustainable supersonic airliner.
Learn more about XB-1’s first flight here.
XB-1 is Boom’s technology demonstrator aircraft and the world’s first independently developed supersonic jet. The aircraft first took flight in Mojave, CA in March 2024. Read more about XB-1 here.
