An SR-71B from NASA's Dryden Flight Research Center in California slices across sky above the snowy southern Sierra Nevada Mountains after being refueled by an Air Force tanker in flight. Capable of flying at more than 2,200 mph and at altitudes of over 85,000 feet, the plane is an excellent platform for research and experiments in aerodynamics, propulsion, structures, thermal protection materials, atmospheric studies and sonic boom characterization.