The U.S. Capitol and Supreme Court were briefly -- and dramatically -- evacuated yesterday when an unidentified plane was reported entering restricted air space about 40 minutes before the jet carrying the remains of former president Ronald Reagan was to land at Andrews Air Force Base.

Legislators and staff members working in the Capitol heard an emergency warning through the building intercom at 4:37 p.m., saying they should exit immediately and get as far away as they could.

Scores of members of Congress and thousands of staffers poured out the doors as police officers shouted, "This is not a drill!"

As they fled, some people dropped briefcases and women flung off high heels. Amy Call, a spokeswoman for Senate Majority Leader Bill Frist (R-Tenn.), said police told people to "run, get out of the Capitol," because of the "imminent" approach of an airplane.

Nearby on the Mall, U.S. Park Police and Capitol Police ordered people to flee. "Do not stop," officers yelled. "Keep moving."

"Ladies and gentlemen, let's move like our lives depend on it. I mean it!" a D.C. police officer screamed.

F-16 fighter jets and Black Hawk helicopters were sent to intercept the errant twin-engine turboprop plane. It turned out to be a Kentucky State Police aircraft ferrying newly elected Gov. Ernie Fletcher (R), a former member of the U.S. House of Representatives, to Washington for Reagan's funeral.

Such small aircraft have generally been off limits at Reagan National Airport since the Sept. 11, 2001, terrorist attacks. But officials said the Kentucky plane was one of several given special permission from the Federal Aviation Administration to land at National for the funeral.

The plane's transponder, which signals its identifying information to ground controllers, was broken, said Brian Roehrkasse, a spokesman for the Department of Homeland Security.

Officials at the FAA command center in Herndon feared that the transponder could have been turned off by a pilot being hijacked, as a distress signal to ground controllers -- or by terrorists trying to disguise the aircraft's identity.

When the plane was about 15 miles southwest of the airport, controllers sounded an alert, FAA spokesman Greg Martin said.

Pilots in the military aircraft identified the Kentucky plane in the air, about eight miles from the airport. The Black Hawks escorted it to the airport runway.

In Washington, the emergency evacuation was called off at 5:08 p.m. "It took a few minutes to sort out the plane was not a threat," Roehrkasse said. "Out of an abundance of caution, security measures were put into place, including the evacuation of the Capitol."