Boeing has decided to pause development and flight plans for the X-66 experimental aircraft, which was central to NASA’s Sustainable Flight Demonstrator (SFD) program aimed at advancing airframe technologies for next-generation, fuel-efficient single-aisle jets, reports AIN.
NASA confirmed the shift in direction, stating that the agency and Boeing are now considering a revised approach that will focus on ground-based testing of long, thin wings—a core feature of the original X-66 design’s transonic truss-braced wing (TTBW) concept.
“Boeing’s proposed focus centers on a ground-based testbed to demonstrate the potential for long, thin-wing technology,” NASA said. The agency explained that development of the more complex X-66 flight demonstrator, which included not only thin wings but also structural bracing, will be paused. Future work on the aircraft may resume depending on the results of the ground tests and further evaluation of the truss-braced configuration.
Initially unveiled by Boeing in January 2023, the X-66 was to be based on a modified McDonnell Douglas MD-90 airframe, outfitted with high-aspect-ratio, composite truss-braced wings mounted above the fuselage. The ambitious plan aimed for a first flight by 2028.
Under a Space Act agreement, NASA had committed $425 million in funding for the SFD project, with Boeing and its industry partners expected to contribute up to $725 million. It remains unclear how much of this funding has been utilized so far.
The change in strategy marks a significant pivot in the program, as NASA and Boeing focus on validating key aerodynamic technologies before committing to a full-scale demonstrator aircraft.
