VERIFICATION
Bell’s X-76 and the Stop/Fold Approach to High-Speed VTOL
Verified as of October 12, 2026
Modern Warfighter reviewed the government records and attributed reporting behind each consequential claim in this article. A Confirmed claim is stated in the cited primary record. A Qualified claim is supported, with its limitation noted beside it.
Verified Claims
CV-22B mission and speed
Confirmed. The National Museum of the U.S. Air Force describes the CV-22B’s mission as long-range infiltration, exfiltration and resupply for special operations forces. Its fact sheet lists a maximum cruising speed of 277 mph, which Modern Warfighter converts to about 240 knots. The figure is a listed specification for the CV-22B variant, not a measured comparison with the X-76.
Record: National Museum of the U.S. Air Force, Bell-Boeing CV-22B Osprey fact sheet
SPRINT objective
Confirmed. DARPA describes SPRINT as a joint DARPA and U.S. Special Operations Command effort to demonstrate an X-plane that cruises at 400 to 450 knots at relevant altitudes and operates from unprepared surfaces. The agency says the results can inform military aircraft of different sizes. These are program objectives, not achieved X-76 performance.
Records: DARPA, SPRINT program page and DARPA, March 9, 2026
Potential missions
Confirmed. DARPA’s FY2027 SPRINT budget description identifies contested logistics and infiltration among the desired military applications of high-speed VTOL. The entry does not assign the X-76 an operational mission.
Record: DARPA FY2027 RDT&E justification, printed p. 1-261 (PDF p. 285)
Design review and flight plan
Confirmed. DARPA announced on March 9, 2026, that the X-76 had completed its critical design review, clearing the way for continued build and ground-test work. The agency plans its Phase 3 flight-test campaign for early 2028. Completing the review does not mean Phase 2 is finished, and early 2028 is a planned campaign, not a confirmed first-flight date.
Record: DARPA, March 9, 2026
Osprey airplane mode
Qualified. The Navy describes the V-22’s nacelles rotating forward for horizontal flight, allowing it to cruise as a turboprop aircraft. NAVAIR’s product record confirms the helicopter and turboprop operating modes. The Navy fact-file passage was read through search retrieval because direct requests to the page were blocked.
Records: U.S. Navy, V-22B Osprey fact file and NAVAIR, MV-22B Osprey product record
Rotor drag and the stop/fold design
Qualified. Cmdr. Ian Higgins, whom DARPA identifies as the SPRINT program manager, told Aerospace Testing International that exposed rotors create drag and limit forward-flight speed. He described Bell’s design shifting lift to the wing as propulsion changes to jet thrust, with the rotors stopping and folding for cruise. This is an attributed account of the intended design. No engine layout, engine supplier or completed free-flight conversion is asserted.
Records: Aerospace Testing International, September 9, 2026 and DARPA, March 9, 2026
Program phases and Bell’s selection
Confirmed. SPRINT entered Phase 1 on November 1, 2023. DARPA awarded Phase 1B preliminary-design contracts to Bell and Aurora Flight Sciences in May 2024, and Bell received the contract for Phases 2 and 3 in June 2025 as the sole performer. DARPA’s March 2026 announcement separately dates the start of Phase 2 to May 2025.
Records: DARPA, SPRINT program page and DARPA, March 9, 2026
Aurora’s fan-in-wing proposal
Qualified. Aurora described its competing proposal as a fan-in-wing aircraft with three embedded lift fans and integrated covers for the transition to forward flight. This is the company’s account of its preliminary design. DARPA independently identifies Aurora as a Phase 1B performer.
Records: Aurora Flight Sciences, May 20, 2024 and DARPA, SPRINT program page
Holloman sled testing
Qualified. Bell announced on February 8, 2024, that it had completed sled testing at Holloman Air Force Base, demonstrating folding-rotor technology, integrated propulsion and flight controls at representative flight speeds. The release gives no numerical speed. Bell’s December 2024 release dates the sled work to 2023.
Records: Bell, February 8, 2024 and Bell, December 4, 2024
Track-guided transition paper
Qualified. Troy Schank, Hong Xin and Albert Brand of Bell presented a 2025 Vertical Flight Society Forum paper on Bell’s Track-Guided Test Vehicle at the 10-mile Holloman High Speed Test Track. The abstract calls the result the “first known powered prop-to-jet and jet-to-prop transition.” That is the authors’ characterization. The abstract gives no test dates or speeds, the full paper was not reviewed, and a track-guided run is not free flight. The Forum’s technical program lists all three authors with Bell.
Records: Vertical Flight Society, Forum 81 paper and Vertical Flight Society, Forum 81 technical program
NIAR wind-tunnel testing
Qualified. Bell reported on December 4, 2024, that wind-tunnel testing at Wichita State University’s National Institute for Aviation Research evaluated stability and control through rotor-fold and rotor-unfold sequences. Bell described the work as risk reduction for a future flight demonstration. Model scale is not specified, and tunnel results are not free flight.
Record: Bell, December 4, 2024
Conversion difficulty and load limits
Qualified. Higgins described the transition between rotor-borne and wing-borne flight as the most challenging part of the design. He said the flight controls must keep the aircraft stable and within component load limits. This is an attributed description of intended control behavior, not a demonstrated result.
Test announcements preceded the design review
Confirmed. Bell’s Holloman and NIAR announcements both preceded DARPA’s March 2026 design-review announcement. The dates establish announcement order only. Bell’s releases do not say how closely their test articles correspond to the final X-76, and their timing does not prove a design mismatch.
Records: Bell, February 8, 2024, Bell, December 4, 2024 and DARPA, March 9, 2026
Uncrewed demonstrator
Qualified. Higgins described the X-76 as uncrewed, with an operator supplying heading and altitude commands and the flight-control computer flying the aircraft. This is an attributed interview account.
Reported test-payload target
Qualified. Aerospace Testing International reported a 1,000-pound payload target used to size the program-defined X-76 test mission. The figure rests on the publication’s account. It is not presented as a verified government requirement, a demonstrated payload or an operational specification.
Planned work before flight
Confirmed. DARPA’s FY2027 SPRINT plan includes structural proof-load testing and airworthiness certification. Software integration lab verification is planned to check the aircraft’s response to simulated failures. Final assembly leads to ground checkout, including engine runs. These are planned activities.
Record: DARPA FY2027 RDT&E justification, printed pp. 1-261 to 1-262 (PDF pp. 285–286)
Source Record
- Defense Advanced Research Projects Agency. Speed and Runway Independent Technologies (SPRINT) program page. Checked October 12, 2026. darpa.mil
- Defense Advanced Research Projects Agency. X-76 critical design review announcement. March 9, 2026. darpa.mil
- Defense Advanced Research Projects Agency. Fiscal Year 2027 RDT&E Budget Justification, Volume 1. April 2026. comptroller.war.gov
- U.S. Navy. V-22B Osprey tilt-rotor aircraft fact file. navy.mil
- Naval Air Systems Command. MV-22B Osprey product record. navair.navy.mil
- National Museum of the U.S. Air Force. Bell-Boeing CV-22B Osprey fact sheet. nationalmuseum.af.mil
- Bell. Bell Demonstrates High-Speed Vertical Takeoff and Landing (HSVTOL) Technology at Holloman Air Force Base. February 8, 2024. bellflight.com
- Bell. NIAR wind-tunnel testing release on stop/fold jet transition. December 4, 2024. bellflight.com
- Aurora Flight Sciences. Preliminary-design announcement for its SPRINT fan-in-wing X-plane. May 20, 2024. aurora.aero
- Vertical Flight Society. Full Scale Stop-fold Transition Demonstration on a High-Speed Test Track, by Troy Schank, Hong Xin and Albert Brand. 81st Annual Forum, May 20, 2025. proceedings.vtol.org
- Vertical Flight Society. 81st Annual Forum technical session program. June 2025. vtol.org
- Aerospace Testing International. Feature on Bell’s X-76 with Cmdr. Ian Higgins, by Paul Metcalfe. September 9, 2026. aerospacetestinginternational.com
- Defense News. Interview with Cmdr. Ian Higgins on SPRINT, by Stephen Losey. December 27, 2023. defensenews.com
Publication Limits
Bell’s Holloman, NIAR and Forum 81 records describe earlier test articles. None reports a complete-aircraft conversion in free flight, and none specifies how closely its test article corresponds to the final X-76.
Higgins told Defense News in December 2023 that SPRINT was then not focused on survivability or potential payload. That earlier statement does not resolve the later test-payload figure. The article publishes no X-76 range, gross weight or engine-supplier figure.
The article’s judgments about the cost of carrying rotor hardware through cruise, and about what the 2028 flights must prove, are Modern Warfighter’s analysis. They are not itemized on this page.