Artist’s concept of the X-66 aircraft. Boeing and NASA have already collaborated on wind tunnel tests, computational fluid dynamics modeling, and structural design and analysis aimed at exploring how best to approach fuel-efficient, sustainable designs. Source | NASA

The X-66 Sustainable Flight Demonstrator (SFD), an X-Plane project with a high-mounted truss-braced thin wing launched in January 2023, is being put on the back burner. Boeing’s (Arlington, Va., U.S.) April 24 announcement that it is making moves to pause the NASA-led (Washington, D.C., U.S.) project have been followed by a report by the agency that both partners are “currently evaluating an updated approach ... that would focus on demonstrating thin-wing technology with broad applications for multiple aircraft configurations.”

To become NASA’s largest X-Plane, the demonstrator was specifically focused on helping the U.S. achieve net-zero aviation emissions by 2050, informing future single-aisles with a new wing rendering — extra-long, thin wings stabilized by diagonal struts known as the transonic truss-braced wing (TTBW) concept. Boeing was working with NASA to build, test and fly a full-scale version, with wing assembly supported by Boeing company Aurora Flight Sciences (Bridgeport, W.Va., U.S.). Though materials were never /confirm/ied, both Boeing and Aurora have extensive composites expertise that could potentially inform the future wing design.