26-04-2025
NASA, Boeing pause X-66 to chase breakthrough ultra-thin wing aircraft design
NASA and Boeing are pausing the development of the X-66 full-scale Sustainable Flight Demonstrator. Instead, they will re-focus their efforts on demonstrating the benefits of thin-wing technology.
Until recently, the US space agency and Boeing touted the X-66 as a great leap for sustainable aviation. That aircraft design featured extra-long, thin wings supported by diagonal struts. Though those plans have been put on ice, they still believe in the benefits of thin-wing technology.
Their new project "would focus on demonstrating thin-wing technology with broad applications for multiple aircraft configurations," NASA explained in a statement.
The re-evaluation would see Boeing focus on a "ground-based testbed to demonstrate the potential for long, thin-wing technology", NASA explained on it website.
The X-66 program heavily modified a McDonnell Douglas MD-90 aircraft to demonstrate a truss-braced version of the thin wing. The experimental aircraft was at the forefront of NASA's plans to achieve net-zero aviation emissions by 2050.
The transonic truss-braced wing (TTBW) aircraft was scheduled to make its first flight in 2028. If flight demonstrations were successful, Boeing planned to start operating the aircraft commercially in the 2030s.
Now, in its statement, NASA says it is 'evaluating an updated approach to the agency's Sustainable Flight Demonstrator project that would focus on thin-wing technology with broad applications for multiple aircraft configurations.'
According to a report by Aviation Week, engineers from the X-66 program are being reallocated to support Boeing's delayed certification of the 777X and 737 MAX variants.
The new development is in line with Boeing's recent cost-cutting strategy as well as its renewed focus on finalizing programs that serve existing customers. Unfortunately, it also reflects the Trump administration's efforts to slash NASA's science budget in half for the upcoming fiscal year.
Still, Boeing claims it still believes in the potential of thin-wing technology to enable efficient, sustainable air transportation.
NASA's original X-66 agreement with Boeing would see it provide $425 million in funding through milestone payments. Boeing and industry partners were set to contribute $725 million toward the project. The new statement doesn't specify whether these details have now changed.
NASA notes that "since NASA issued the Sustainable Flight Demonstrator award in 2023, the project has made significant progress toward its goal of informing future generations of more sustainable commercial airliners."
Under the new proposal, "all aspects of the X-66 flight demonstrator's design, as well as hardware acquired or modified for it, would be retained while the long, thin-wing technology is being investigated with more focus. NASA and Boeing would also continue to collaborate on research into the transonic truss-braced wing concept."
