X-48B

Another scale model, the 500-pound X-48B made its first flight in July 2007. This spring, the remotely controlled, Boeing-built aircraft, which features a "blended wing" body (wingspan: 21 feet), made its 80th flight as it completed the first phase of its testing.

Test flights are expected to resume later this year, after a new computer is installed. Unlike most other X-Planes, the X-48B isn't designed for supersonic flight; rather, it's meant to study ways to create quieter, more fuel-efficient aircraft.