Knives 'hidden on planes for weeks'

Restrictions on carry-on items were tightened after 11 September 2001

United States authorities took five weeks to uncover box cutter knives and other suspicious items that had been placed on two planes, the student at the centre of a security breach investigation has said.

Nathaniel Heatwole, 20, said that he had placed the knives and a mock-up bomb on board two specific Southwest Airlines flights back in September and sent an e-mail to the Transportation Security Administration (TSA) outlining what he had done.

Mr Heatwole, who is due to appear in court in Balitmore on Monday, said his was an act of civil disobedience aimed at highlighting security flaws and improving public safety.

Federal authorities say they are going to charge Mr Heatwole with bringing a dangerous weapon aboard an aircraft.

Whatever the motivation the BBC's Adam Brookes in Washington says the authorities have yet to explain how the items escaped detection for more than a month.

E-mail tip off

It was last week that maintenance staff aboard the two airliners found the mock explosive devices and box cutters - the sort of knives used by the 11 September hijackers - hidden in the toilets.

Thousands of planes were checked in the wake of the discovery

Security checks were ordered for every commercial airliner in the US after the items were discovered.

According to a Federal Bureau of Investigation affidavit obtained by the Associated Press Mr Heatwole - a student in North Carolina - told agents he went through normal security procedures at airports in Baltimore and Raleigh-Durham, North Carolina, carrying the banned items in plastic bags.

The TSA received an e-mail from Mr Heatwole on 15 September claiming that he had "information regarding six security breaches" at the two airports between 7 February and 14 September, the affidavit said.

"The writer stated that he smuggled several items on his person and some in his carry-on bag," the Associated Press quoted it as saying.

"The e-mail author also stated that he was aware his actions were against the law and that he was aware of the potential consequences for his actions," it added.

The items found aboard the two planes - one in New Orleans, the other in Houston - included box cutters, clay that resembled plastic explosives and bleach, sources familiar with the investigation said.

The liquid was contained in suntan lotion bottles; the clay was inside Play-Doh containers.

Southwest Airlines said notes found with both packages said the intention was to simulate a threat and to challenge the security screening procedures for passenger planes.