Air security better post-9/11, but vigilance needed: U.S.

LONDON (Reuters) - Most but not all of the 19 September 11 attackers would have been picked up beforehand if today's air travel security had been in place, so vigilance is still needed, Homeland Security Secretary Janet Napolitano said on Tuesday.

"We think that with many of the rules on travel and screening that have been put into places since 9/11, all but four of the 9/11 attackers would have been picked up," Napolitano, on a tour of Europe and the Gulf, told reporters.

"So there's been a lot of progress made. But I said 'all but four'. So again you cannot thermoseal the entire United States of America. It means we have to be ever vigilant."

The Department of Homeland Security was created in response to the attacks on the United States on September 11, 2001, when al Qaeda hijackers commandeered four planes, slamming two into New York's World Trade Center and one into the Pentagon outside Washington. The fourth crashed in a field in Pennsylvania.

The United States now requires operators of international flights to and from the United States to electronically provide full advance manifests of their passengers and crew before departure, to keep suspected terrorists off such flights.

Napolitano, who has already visited Ireland, said she would also travel to Portugal, Spain and Kuwait to discuss aviation security, cyber security and violent extremism.

She said the issue of terrorism "is always with us."

"I wake every morning with the belief that terrorism is there and that there are those who seek to harm us and they are looking for ways to do so. I don't have the wherewithal to say we have taken care of that issue. The issue is how to minimize the risk."

She agreed in answer to questions that Somalia and Yemen were of growing concern as sites of militant activity, but declined to elaborate.

(Reporting by William Maclean, editing by Sonya Hepinstall)