The all-clear came within minutes when two fighter jets intercepted the small twin-engine propeller-driven plane eight miles northeast of the Capitol. The alert ended before evacuations were complete at the White House.
The White House briefly went to red alert — its highest level, presidential spokesman Scott McClellan said.
The private turboprop entered restricted airspace northeast of Reagan National Airport, according to federal aviation officials. Jets scrambled from Andrews Air Force Base, Md., intercepted the plane and, as of 6:45 p.m. EST, escorted the plane to Winchester, Va., where it landed without incident.
An aircraft could be heard overhead at the Capitol, in an area customarily closed to aircraft.
Sen. Tom Harkin, D-Iowa, said Capitol Police notified senators' offices: "This is an emergency message ... Capitol Police are tracking unidentified aircraft."
At the White House, Bush had left the Oval Office for the day and was in the residence when the alert sounded. "The president was temporarily relocated," McClellan said. Some senior staff also were seen hurrying from the West Wing to the residence area where a bomb shelter is located.
"We started to relocate some staff," McClellan said. "Officers were prepared to activate the (White House-wide) alert system but we received notification from the jets that were scrambled that the plane had turned away from the White House."