The terror alert system in the nation's capital was put to the test by a small plane that flew within three miles of the White House, leading to the frantic evacuation of government buildings.

Former Homeland Security Secretary Tom Ridge (search) praised security officials for what he said was a quick, appropriate response to divert the wayward pilot away from Washington landmarks.

"It was a successful intervention by the Department of Homeland Security (search), by the Department of Defense," Ridge said Thursday on NBC's "Today" show. "They saw it was a Cessna, saw it was a single-engine plane, and they took care of it."

Alert levels at the White House and Capitol were raised to their highest state Wednesday when the Cessna 150 (search) crossed into restricted air space and failed to respond to a Homeland Security helicopter scrambled to stop it. Military jets fired four warning flares at the aircraft, which was carrying a pilot and a student pilot from Pennsylvania to North Carolina.

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

Lt. Col. Tim Lehmann (search), one of the F-16 fighter pilots who tracked the Cessna, said it wasn't viewed as a high threat and he wasn't ordered to use lethal force.

"So that order was never given to shoot it down," he said in a televised interview.

However, Lehmann said, "That airplane would not have penetrated, it would not have hit anything in D.C. And it would have been dropped from the sky before that would have happened."

The scare, which lasted about 45 minutes, sparked a frenzy of activity that tested the capital's post-Sept. 11 response system. Homeland Security officials said smooth coordination among a handful of federal agencies to share information and quickly scramble warplanes showed the system worked as designed.

"Security measures were effectively executed," Homeland Security spokesman Brian Roehrkasse said.

President Bush, biking with a high school friend at the Patuxent Wildlife Research Center in Beltsville, Md., was unaware of the midday scare as it was occurring. His security detail knew of the raised threat level.

White House spokesman Scott McClellan said Thursday the Secret Service is reviewing its response to the threat, but he defended the decision to not immediately alert the president.

"The president was never considered to be in any danger," McClellan said.

There were complaints elsewhere, however. Mayor Anthony Williams (search) said city officials weren't told about the threat until the all-clear was sounded, more than 10 minutes after the White House and Capitol were evacuated. A city government building that houses the mayoral and District of Columbia Council offices, located two blocks from the White House, was not evacuated.

"Critical and potentially life-or-death information about threats facing district residents needs to be shared immediately, not five, 10 or 15 minutes after the fact," Williams said.

While praising the fast federal response, experts said the alarm highlighted holes in security measures.

David Heyman, homeland security director at the Center for Strategic and International Studies in Washington, said more needs to be done to prevent unauthorized flights and protect restricted airspace.

"The scare reminds us both of the challenges we still face in securing our nation's skies as well as the significant steps we've taken to protect against future attacks," Heyman said.

"We have more work to do."

The incident began at 11:28 a.m. when Federal Aviation Administration radar picked up the small, two-seater aircraft. Gainer said the first alert went out when the plane was 21 miles — about 17 minutes flying time — from the city.

One Black Hawk helicopter and one Cessna Citation jet, assigned to the U.S. Customs and Border Protection, were dispatched at 11:47 a.m. from Reagan National Airport. Authorities said the Citation established communication with the Cessna's pilot around 12:06 p.m. as two F-16 jet fighters moved in. The jets, scrambled from Andrews Air Force Base in Maryland, fired four warning flares before the plane turned away.

"If he wouldn't have responded, intentionally or not, he could have been shot down," said Master Sgt. John Tomassi of the North American Aerospace Defense Command in Colorado Springs, Colo.

The plane then turned to the west and the warplanes escorted it to the airport in Frederick, Md., where the men aboard were taken into custody shortly after 12:38 p.m. The government decided not to press charges after interviewing the men and determining the incident was an accident.

"They were navigating by sight and were lost," Justice Department spokesman Kevin Madden said. The men were identified as Hayden Sheaffer of Lititz, Pa., and Troy Martin of Akron, Pa., who were on their way to an air show in Lumberton, N.C.

Homeland Security officials said the alarm marked the first time the public has been told that terror alert levels were raised to red.

At the White House, the Secret Service raised the alert level to red for eight minutes, starting at 12:03 p.m., as the Cessna moved within 10 miles, McClellan said. Vice President Dick Cheney, first lady Laura Bush and former first lady Nancy Reagan, overnighting at the White House for a special event, were moved to secure locations.

Capitol Police put the Capitol on red alert at 12:04 p.m. Lawmakers, tourists and reporters raced out of the building.