Sharp-eyed observers have spotted flocks of the Air Force's most secret fighter jets flying over Southern California in recent weeks, providing the first glimpses of an aircraft that has remained shrouded in mystery for more than 10 years, according to an authoritative defense industry magazine.

Groups of 10 F-117 Stealth fighter jets have been seen during daylight hours streaking over Mojave, a small town outside Edwards Air Force Base about 90 miles north of Los Angeles, Aviation Week and Space Technology reported in its May 1 issue.After flying the F-117 for five years, the Air Force last November unveiled the aircraft to the public for the first time. The plane uses special designs and materials to elude detection by radar.

At that time, the service said that it wanted to begin daytime flights of the batlike warplane and acknowledged that such training flights would lead to sightings by civilians. Until recently, the Air Force had been flying the aircraft under cover of night in an effort to keep details of the planes a secret.

The Air Force, which has remained secretive about most details of the plane, said Friday that it would not discuss operational matters regarding the program.