An American Airlines plane, searched at Richmond International Airport after a passenger found a letter saying a bomb was on board, reached its final destination without incident after being detained for four hours.

American Airlines Flight 874 left Dallas-Fort Worth Airport about 2 p.m. EST Thursday en route to Richmond with Norfolk scheduled as its final destination.Mary O'Neill, an American Airlines spokeswoman in Dallas, said that as the plane neared Richmond, a passenger discovered the note saying a bomb was on board the plane.

"That passenger gave that to a flight attendant who then gave it to the captain," O'Neill said. "The pilot elected to go ahead and land at Richmond rather than divert to another airport."

The airliner, a McDonnell Douglas MD-80 twin-jet, landed in Richmond at 4:34 p.m. and 125 passengers and crew were taken off the plane within five minutes of landing.

O'Neill said FBI and Virginia State Police were on the scene. Investigators brought in dogs to search the plane. Officials interviewed passengers and crew members once the search was completed.

Airport and aviation safety officials throughout the world have been on alert after a bomb destroyed Pan Am Flight 103 and killed 270 people in Lockerbie, Scotland, last week.

This is the second such incident for American Airlines in one week.

On Tuesday, American Airlines Flight 240, a Boeing 767 en route from San Francisco to Dallas-Fort Worth airport was diverted to Albuquerque International Airport when a University of California-Berkeley lecturer handed a flight attendant a note suspected of being a bomb threat.

Peter Canning, 40, was arrested and charged with conveying false information, but the charges were dismissed Thursday after an 11-year-old San Francisco boy admitted that he wrote the threatening note.