U.S. no-fly list doubles in year

The Tribute in Lights is illuminated on the skyline of lower Manhattan at dusk during events marking the 10th anniversary of the 9/11 attacks on the World Trade Center in New York, September 11, 2011.

WASHINGTON (Reuters) - The number of people banned from flying under the U.S. government's terrorism watch list has more than doubled over the last year, a counterterrorism source said on Thursday.

The list banning people from flying to the United States or from flights within the country, has risen to about 21,000 names from about 10,000, said the source, who spoke on condition of anonymity to discuss security matters.

The increase is largely due to the failed Christmas Day 2009 bombing of a Northwest Airlines airliner headed for Detroit. The attempt resulted in a government examination of the list and a widening of those who could be put on it, the source said.

"Certainly, the review after Christmas Day was one of the big factors," said the source.

A review of files led to putting people on the list who would be a threat to U.S. security, not just to aviation. Names were also added if there was proof that the person had attended a guerrilla training camp, the source said.

The no-fly list is produced by the FBI's Terrorist Screening Center. The aviation list is a subset of a larger list of suspected extremists.

The United States also is working with "foreign partners" to compile names, the source said, adding: "It's really a combination of factors."

A spokesman for the Transportation Security Administration declined to comment.

The increase has come even as President Barack Obama's administration said it is closer than ever to defeating al Qaeda extremists and has killed many of its leaders.

(Reporting By Ian Simpson; Editing by Paul Thomasch)