PALMDALE - The once top-secret Blackbirds on display in Palmdale have a new nest mate: the F-117A Nighthawk, also known as the stealth fighter. The dart-shaped aircraft, the fourth of its kind built and used solely for testing, was moved into display position Monday at Blackbird Airpark, taking its place beside other former "black" aircraft, the SR-71 and U-2. "Look at how many black airplanes you can come see right here," said Fred Johnsen , curator of the Air Force Flight Test Center Museum, of which Blackbird Airpark is a satellite. Escorted by members of the 410th Flight Test Squadron,...