A U.S. Airways flight was diverted on Monday after a "threatening note" was discovered on the plane, the Transportation Security Administration said.

The plane, flight 3441, which was carrying 56 people en route from Philadelphia in the eastern state of Pennsylvania to Houston, Texas, in the south, was diverted to the Bristol Tri-Cities Airport in the southern state of Tennessee.

The flight landed without incident. The passengers and crew were questioned by FBI officers after leaving the plane, and explosives teams were searching the plane.

A FBI spokesman said the aircraft's pilot reported suspicious activity on the plane, and that the plane was diverted to the airport.

The United States has tightened air security since British authorities announced earlier this month they had foiled a plot to blow up passengers planes from Britain to the United States, and there have been several scare incidents concerning U.S. passengers planes since then.

(Xinhua News Agency August 29, 2006)