The US National Aeronautics and Space Administration (Nasa) has announced that its Sustainable Flight Demonstrator aircraft, to be built and partly funded by Boeing, has been officially designated the X-66A. This makes it the latest in the renowned US series of X-plane experimental and technology demonstrator aircraft, which started with the Bell X-1 rocket plane, which, in 1947, became the first piloted aircraft to exceed the speed of sound in level flight.

Authority for awarding X-plane designations is vested in the US Air Force, even if the aircraft concerned is devoted to purely civil aerospace research. Nasa and Boeing jointly applied for X-plane status for their project, shortly after they announced it, earlier this year.

“The Sustainable Flight Demonstrator builds on Nasa’s world-leading efforts in aeronautics as well as climate,” affirmed Nasa administrator Bill Nelson. “The X-66A will help shape the future of aviation, a new era where aircraft are greener, cleaner, and quieter, and create new possibilities for the flying public and American industry alike.”

The X-66A will be a full-scale aircraft, to support the development of a new generation of single-aisle airliners – the workhorses of the world’s airlines – that will be more sustainable (that is, produce fewer greenhouse gas emissions, through the use of less fuel or by using cleaner power sources, or a mixture of both). Its design concept is what is called a transonic truss-braced wing. That is, its wings will be extra-long and thin and will be braced by diagonal struts.

To build the X-66A, Boeing will take the fuselage of an MD-90 airliner and shorten it, and then fit it with totally new wings and new engines. Nasa is investing $425-million in the project, while Boeing and its partner companies will be contributing a further $725-million.

“To reach our goal of net zero aviation emissions by 2050, we need transformative aircraft concepts like the ones we’re flying on the X-66A,” highlighted Nasa Aeronautics Research Mission Directorate associate administrator Bob Pearce. “With this experimental aircraft, we’re aiming high to demonstrate the kinds of energy-saving, emissions-reducing technologies the aviation industry needs.”