US airliners grounded after security scare

All commercial aircraft in the United States were being searched last night after box cutters, similar to those used during the 11 September hijacks, were discovered on two Southwest Airlines planes.

Law enforcement authorities said that the box cutters were probably left by people wanting to test airline security. The FBI is investigating how plastic bags containing box cutters and items such as clay, matches, and bleach got on the planes. They were discovered during maintenance by airline employees on Thursday on two Boeing 737 aircraft in Houston and New Orleans.

Southwest said notes accompanied the packages indicating the items were intended to challenge checkpoint security procedures. Robert Mueller, the director of the FBI, said: "It does not appear to be a terrorist event. There were no explosives, there was no imminent threat in terms of a capability to commit a terrorist act."

Box cutters have been banned as carry-on items after being used as weapons during the 11 September attacks in 2001. Liquid bleach is not permitted on commercial flights, but some matches and clay are allowed.

The Federal Aviation Administration said the inspection of nearly 6,000 planes over 24 hours was not expected to cause flight delays. Southwest said it had completed inspections of its fleet of 385 aircraft and no suspicious items had been found.