NASA Administrator Michael Griffin, right, meets with aerospace engineer Burt Rutan Wednesday, April 20, 2005 at NASA Headquarters in Washington. Photo Credit: (NASA/Renee Bouchard)

The Voyager aircraft circles before landing at Edwards Air Force Base, Edwards, California, to complete its record breaking, nonstop unfueled flight around the world.

The AD-1 aircraft with its wing swept. Visible are the twin jet engines that powered the aircraft and the fixed landing gear.

AD-1 in flight. Flight #30. The AD-1 aircraft in flight with its wing swept at 60 degrees, the maximum sweep angle.

Multiple exposure image showing wing movement on AD-1.

The Proteus high-altitude aircraft on the ramp at the Mojave Airport in Mojave, California.

The uniquely shaped Proteus high-altitude aircraft soars over California’s Mojave Desert during a July 1999 flight.

The uniquely-shaped Proteus high-altitude research aircraft lifts off from the runway at the Mojave Airport in Mojave, California.

The unusual design of the Proteus high-altitude aircraft, incorporating a gull-wing shape for its main wing and a long, slender forward canard, is clearly visible in this view of the aircraft in flight over the Mojave Desert in California.

The unusual design of the Proteus high-altitude aircraft, incorporating a gull-wing shape for its main wing and a long, slender forward canard, is clearly visible in this view of the aircraft in flight over the Mojave Desert in California.

A frontal view of the Proteus high-altitude aircraft on the ramp at the Mojave Airport in Mojave, California in July 1999.

The cockpit and instrument panel of the AD-1 aircraft. Due to the small size of the AD-1, instrumentation was limited and the cockpit was cramped.

Research pilot Richard E. Gray, standing in front of the AD-1 Oblique Wing research aircraft.