Fighter jets scrambled over Washington and authorities hurriedly evacuated the White House and the US Congress yesterday when an unidentified plane roamed into restricted airspace, sparking fears of a September 11-style attack.
The light private Cessna ignored calls from air traffic controllers and entered the restricted air zone around Washington, coming within five kilometres of the White House before turning away, authorities said.
The plane's approach sent two F-16 fighter jets into the air over the US capital and thousands of staff and tourists into the streets outside the White House, Capitol building and Supreme Court in an urgent evacuation.
President George W. Bush was on a bicycle ride at a suburban wildlife preserve at the time, but Vice President Dick Cheney was quickly evacuated, White House spokesman Scott McClellan said.
First lady Laura Bush and former first lady Nancy Reagan, who was visiting, were rushed to a secure location on the White House grounds, he said.
The two fighters, which scrambled from nearby Andrews Air Force base, intercepted the Cessna and fired four flares to get the pilot's attention before escorting the plane to Frederick, Maryland, officials said. The pilot and a passenger were taken into police custody.
The US Customs service also scrambled Black Hawk helicopters during the alert, which the White House characterised as the most serious since the September 11, 2001, attacks by hijacked airliners in New York and Washington.
"Get out, get out," Capitol police shouted to lawmakers and staff as they moved through the building and adjacent offices, clearing the floors and galleries in both chambers.
US senators debating highway legislation dropped their papers and ran from the chamber. House of Representatives lawmakers were in the midst of a vote when the evacuation order came.
Capitol police swiftly moved senators, aides, lobbyists and journalists toward Union Station, about two blocks away. Police used bullhorns to order onlookers near the Capitol to "stay away from the building."
The incident prompted the government's joint operations centre to send an "alert" to White House staff. "Do not leave building. Proceed to interior halls and lower levels. Avoid windows," the alert read.
The Secret Service and Capitol police gave the "all clear" 15 minutes after the first alert and allowed staff to return to their offices.
The plane, a single-engine two-seater Cessna 152, originated at a small airport in Smoketown, Pennsylvania.
Pilots are not allowed to fly into airspace set up by the Federal Aviation Administration after the September 11 attacks.
If warnings are ignored and the aircraft remains in restricted airspace it could be shot down. All pilots with permission to fly into or through Washington airspace - mainly commercial flights - must transmit special identification codes to air traffic controllers.
Since September 11, various Capitol buildings have been evacuated for a range of security reasons, from fears of anthrax to bomb threats.