WASHINGTON - Boeing is pumping the brakes on its experimental X-66 flight demonstrator.
The aircraft—being developed with a transonic truss-braced wing—is on “pause for later consideration” after Boeing proposed to focus on a ground-based testbed, which will instead demonstrate simpler, thin-wing technology, Jack Daleo writes for Flying.
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The Military & Aerospace Electronics take:
5 May 2025 - “We have learned a lot in the past few years partnering with NASA on the X-66 program that will influence the future generations of airplane design,” the company said in a statement shared with FLYING. “Going forward, we will focus efforts on the single most-promising design feature of the X-66 configuration—the thin-wing design. What we learn with this approach can be applied across multiple products, including potential truss-braced wing configurations and beyond.”
The development was originally part of a $1.15 billion effort under a 2021 Space Act Agreement to advance sustainable flight technologies. NASA committed $435 million over seven years, with Boeing covering the remaining $725 million.
The X-66, based on a modified McDonnell Douglas MD-90, was intended to test a thin, truss-braced wing design aimed at reducing drag and fuel consumption. Boeing now plans to halt the demonstrator and focus instead on applying the wing technology more broadly, citing lessons learned from the Sustainable Flight Demonstrator program.
Related: Boeing begins X-66 modification for NASA's Sustainable Flight Demonstrator project
Related: Mysterious X-37B 'space plane' is returning to orbit, and for once we're being told why
Jamie Whitney, Senior Editor
Military + Aerospace Electronics
