The experimental aircraft being developed for DARPA’s high-speed vertical take-off and landing program has been officially designated the X-76 and is now under construction by Bell Textron.
The designation was revealed as the Speed and Runway Independent Technologies (SPRINT) program passed a Critical Design Review (CDR), clearing the demonstrator for manufacturing, integration, assembly and ground testing. Flight testing is planned to begin in early 2028 under a third phase of the program.
SPRINT is a joint effort between DARPA and US Special Operations Command (SOCOM) to develop an aircraft that combines the cruise speed of a fixed-wing jet with the vertical lift capability of a rotorcraft, without relying on prepared runways. The X-76 aims to demonstrate cruise speeds exceeding 460mph (740km/h), hovering in austere environments and operations from unprepared surfaces.
The X-76 designation places the demonstrator within the historic lineage of experimental aircraft used to push the boundaries of aviation. The out-of-sequence number – the last X-plane designation assigned was X-68 – was chosen to coincide with the country’s 250th anniversary, as a nod to the revolutionary spirit of 1776.
Cmdr. Ian Higgins, US Navy, DARPA SPRINT program manager, said, “For too long, the runway has been both an enabler and a tether, granting speed but creating a critical vulnerability. With SPRINT, we’re not just building an X-plane, we’re building options. We’re working to deliver the option of surprise, the option of rapid reinforcement, and the option of life-saving speed, anywhere on the globe, without needing any runway.”
Bell’s design uses a stop-fold tiltrotor configuration, in which the aircraft takes off and hovers using tilting rotor nacelles before the rotors gradually stop, fold back along the nacelles and propulsion transitions to turbofan-based thrust for high-speed cruise. The concept was validated on a sled track at Holloman Air Force Base in 2023 and through wind tunnel testing at Wichita State University in 2024.
Phase 2 of the program began in May 2025 after Bell’s design was selected over Aurora Flight Sciences. DARPA has requested US$55.2 million in fiscal year 2026 funding to continue advancing the program.
Data collected during the X-76 flight test campaign will be used to evaluate the feasibility of high-speed vertical lift aircraft and inform future acquisition decisions by SOCOM and other branches of the US military.
