Authorities raised the terrorist threat assessment over the weekend after new intelligence indicated that operatives of Osama bin Laden’s al-Qaida terror network, possibly trained and licensed to fly passenger jets, may now be pilots for some foreign airlines, ideally positioning them to carry out suicide attacks, U.S. officials told NBC News on Monday.

Reinforced cockpit doors intended to thwart hijackers after the Sept. 11, 2001, terrorist attacks would now protect any terrorist pilot at the controls, the officials said on condition of anonymity.

Authorities would not describe the terror threats in detail publicly, but the U.S. officials told NBC’s Jim Miklaszewski that the threat alert would remain at “orange,” or high, through the end of January, which they said was an indication of its seriousness. 

Al-Qaida may have dirty bomb

New intelligence indicates that al-Qaida remains intent on attacking large gatherings of people with chemical or biological weapons, official said. They said law enforcement agencies were looking closely at two rural locations — one in the East and the other in the Southwest — that were believed to be high on the terrorist target list.

Most troubling, the officials sad, were indications that al-Qaida may already possess a radiological weapon, or so-called “dirty bomb.” They did not elaborate.

Experts said a potent dirty bomb could spread radioactive material for a half-mile in all directions. People in the fallout zone would be bombarded with radiation levels that they would not otherwise be exposed to from natural sources for a full year.

While it may not particularly deadly, the psychological impact of a dirty bomb could be devastating, experts said.

"The point of a dirty bomb is not mass casualties,” terrorism specialist Roger Cressey, chief of staff for President Bush’s Critical Infrastructure Protection Board from November 2001 to September 2002, said in an interview. “It's much more to instill fear and panic into the general population."

Bush, Ridge: Be vigilant
President Bush nonetheless urged people Monday to “go about their lives.”

“Our government is doing everything it can to protect our country,” Bush said at a ceremony marking the Jewish celebration of Hanukkah. “American citizens need to go about their lives, but as they do so, they need to know that governments at all levels are working as hard as we possibly can to protect the American citizens.”

Homeland Security Secretary Tom Ridge made the rounds of the nationally broadcast news shows Monday morning as most Americans returned to work a day after the government raised the warning.

“I think it’s very, very important to send a message to the terrorists of goodwill and resolve,” said Ridge, who said the Bush administration wanted people to “be vigilant and have a good communications plan under way.”

The upgrade from “yellow,” or “elevated,” followed warnings that the al-Qaida terrorist organization could be plotting attacks against the United States during the holidays. 

“The information we have indicates that extremists abroad are anticipating near-term attacks that they believe will either rival or exceed” the Sept. 11, 2001, attacks, Ridge had said in announcing the upgraded alert status Sunday.

Some of the intelligence information indicated that al-Qaida was seeking to use planes as weapons again, he said. Ridge said the terrorists were “constantly evaluating procedures ... to find gaps in our security posture that could be exploited.”

In Miami, a man was arrested Monday at the main airport with a hacksaw and a razor blade in his shoe.

Information comes from ‘many sources’
Ridge said Monday that the alert was changed because of information the United States received from “many sources,” although he said he could not be more specific. “I think over the course of my two-plus years [as head of Homeland Security], there has probably been some reference to just about every major metropolitan area,” he said.

A U.S. official said on condition of anonymity Sunday that some of the intercepted communications and other intelligence mentioned New York, Washington and unspecified cities on the West Coast. Authorities also are concerned about dams, bridges, nuclear plants, chemical facilities and other public works.

Thousands of state and local law enforcement agencies have received an FBI advisory urging special notice of potential security upgrades and of sites that could be targets, the official said. Ridge contacted his counterparts in Canada and Mexico about increasing border security.

Ridge said Monday of intelligence reports on CBS’s “Early Show": “The volume is up. The quality of the reporting is up. The credibility is there.”

In another indication that the administration was taking the alert seriously, Defense Secretary Donald Rumsfeld returned Monday to the Pentagon from his ranch in New Mexico, where he had begun his Christmas vacation over the weekend.

No connection to Saddam arrest seen
At a hastily arranged news conference Sunday, Ridge said credible intelligence sources “suggest the possibility of attacks against the homeland around the holiday season and beyond.”

Shortly thereafter, the State Department issued a worldwide caution warning U.S. citizens overseas that they could be terrorist targets. Echoing Ridge, the caution said officials “expect al-Qaida will strive for new attacks designed to be more devastating” than the Sept. 11 attacks.

Ridge said officials did not see a connection between the recent capture of former Iraqi President Saddam Hussein and the heightened security alert. L. Paul Bremer, the U.S. administrator in Iraq, backed that up Monday, telling NBC News that he saw no connection.

“No, I think as Secretary Ridge pointed out, there’s been a suggestion of high terror threats certainly in Iraq, where we are on the front of the war on terror over the last weeks, unrelated to Saddam’s capture,” Bremer said.

Ridge tried to reassure Americans traveling by plane for the holidays. “Make no mistake about it: Aviation is far more secure than it’s ever been in the history of the country,” he said. At the same time, Ridge said, security at airports could be ramped up a bit more.

As a result of the change in threat level, all federal departments and agencies were putting action plans in place and stepping up security at airports, border crossings and ports, Ridge said.

“Extensive and considerable protections have been or soon will be in place all across the country,” Ridge said. “Your government will stand at the ready 24 hours a day, seven days a week, to stop terrorism during the holiday season and beyond.”

And he urged Americans not to disrupt holiday plans. “If you’ve got travel plans, travel,” he said.