For Renny Rogers, it was strange enough that military jets were flying low over his home in Waldorf in the middle of the night. It was what he thinks he saw when he headed outside to look early yesterday that floored him.

"It was this object, this light-blue object, traveling at a phenomenal rate of speed," Rogers said. "This Air Force jet was right behind it, chasing it, but the object was just leaving him in the dust. I told my neighbor, 'I think those jets are chasing a UFO.' "

Military officials confirm that two F-16 jets from Andrews Air Force Base were scrambled early yesterday after radar detected an unknown aircraft in area airspace. But they scoff at the idea that the jets were chasing a strange and speedy, blue unidentified flying object.

"We had a track of interest, so we sent up some aircraft," said Maj. Douglas Martin, a spokesman for the North American Aerospace Defense Command in Colorado, which has responsibility for defending U.S. airspace. "Everything was fine in the sky, so they returned home."

At the same time, military officials say they do not know just what the jets were chasing, because whatever it was disappeared. "There are any number of scenarios, but we don't know what it was," said Maj. Barry Venable, another spokesman for NORAD.

Radar detected a low, slow-flying aircraft about 1 a.m. yesterday, according to a military official. Controllers were unable to establish radio communication with the unidentified aircraft, and NORAD was notified. When the F-16s carrying air-to-air missiles were launched from Andrews, the unidentified aircraft's track faded from the radar, the military official said, speaking on condition of anonymity.

Pilots with the D.C. Air National Guard's 113th Air Wing, which flew the F-16s from Andrews, reported nothing out of the ordinary, NORAD officials said.

"It was a routine launch," said Lt. Col. Steve Chase, a senior officer with the wing, which keeps pilots and armed jets on 24-hour alert at Andrews to respond to incidents as part of an air defense system protecting Washington after the Sept. 11 terrorist attacks.

Rogers remains convinced that what he saw was not routine. "It looked like a shooting star with no trailing mist," he said. "I've never seen anything like it."