WASHINGTON -- The White House, the Supreme Court and the U.S. Capitol were briefly evacuated yesterday at noon after a single-engine, two-seater Cessna airplane entered restricted air space over the capital before being forced away by military jets.

		Related coverage See a graphic that shows how events unfolded yesterday. Not just another slow day in Smoketown

White House spokesman Scott McClellan said the plane, owned by an air club and flown from Smoketown, Lancaster County, Pa., came within three miles of the White House, triggering a "red alert," the highest post-Sept. 11 threat level.

When pilot Hayden Sheaffer of Lititz failed to respond to a radio command, F-16s fired four flares at the plane. A Black Hawk helicopter had also joined in pursuit of the Cessna.

The plane appeared to be "on a straight-in shot toward the center of the Washington area," said Capitol Police Chief Terrance W. Gainer.

If the pilot had not veered away, White House officials said, military officials could have ordered it to be shot down. From three miles away, the Cessna 152 could have reached the White House in less than two minutes, depending on its speed.

The Justice Department said the government would not prosecute the two men because the incident was a mistake.

"They were navigating by sight and were lost," said Justice Department spokesman Kevin Madden.

After the plane was escorted to Frederick, Md., the all-clear signal was given at the White House about 11 minutes after the red alert had been sounded at 12:03 p.m.

Machine-gun wielding Secret Service agents and armed police officers told office workers that they could return to work. Emotions ranged between vexation from being frightened and told to run fast to relief that all was well. On Capitol Hill, workers were not permitted to return to their offices until 12:40 p.m. Adjacent streets were blocked for some time after that.

President Bush was bicycling at Patuxent Wildlife Research Center in nearby Beltsville, Md., at the time of the White House evacuation. A fellow cyclist, Mike Woods, a friend of Bush's since high school, told reporters that neither he nor the president was told anything about the evacuation during their ride.

McClellan said the president was notified by his Secret Service detail shortly before noon. Bush later declined to discuss the incident with reporters.

Vice President Dick Cheney, first lady Laura Bush and former first lady Nancy Reagan were all in the White House at the time of the incident. The women were taken to an underground bunker on the premises. Cheney's motorcade was seen speeding out of the White House gates, enroute to a designated "secure location."

The last time that a plane entering restricted air space caused such concern was last summer, when Mrs. Reagan was in Washington for the funeral of her husband, former President Ronald Reagan. The White House and the Capitol were briefly evacuated then after a plane carrying Kentucky Gov. Ernie Fletcher to the services entered the district's restricted zone because some officials didn't realize that it had been cleared to do so.

In 1994, a Cessna crashed into the southwest corner of the White House, damaging it and an old magnolia tree. The pilot -- who is believed to have been deliberately intending to hit the White House -- was killed.

In April, Bush was briefly escorted to the White House bunker and Cheney was taken off the White House grounds when a radar blip was momentarily mistaken as a sign of a plane heading there. Three years ago, Cheney and White House Chief of Staff Andrew Card were evacuated when a Cessna came within four miles of the White House.

Since the Sept. 11 attacks, general aviation planes have not been permitted to land or take off from Washington Reagan National Airport, a few miles from the White House in northern Virginia, or to come within a 15.7-mile radius of the Washington Monument. Pilots complain that the restricted airspace can make for difficult maneuvering for planes flying up and down the eastern U.S. corridor.

White House officials insisted that the response to yesterday's "red alert," showing that the air defense system over Washington was adequate. But many workers in the White House West Wing and the Old Executive Office Building next door did not leave, and many did not even know about the alert. Moreover, the White House internal emergency notification system did not sound. McClellan said there would be an investigation to find out why.

Gainer of the Capitol Police told reporters that more than 25,000 people were evacuated from the Capitol in fewer than six minutes. He admitted that the evacuation caused havoc but said officials had no choice except to take the actions they did. He said there were no serious injuries reported, although he wasn't surprised to hear of some falls and turned ankles. One person was taken away in an ambulance.

Gainer said Capitol Police began monitoring the situation at 11:59 a.m., when the Federal Aviation Administration reported to the Secret Service that a plane had entered restricted airspace "squawking a proper code" but not giving authorities the information they needed to determine whether it was authorized to be so close to the White House.

House Minority Leader Nancy Pelosi, D-Calif., praised Capitol Police for their handling of the evacuation. "Better safe than sorry," she said. "The evacuation took place with dignity, with great speed and with respect for all in the Capitol."

Department of Homeland Security officials promised a thorough investigation and evaluation of the event and whether the correct decisions had been made. The inquiry is to include various scenarios of what might have happened if the incident had not been an apparent accident.