The Bush administration lowered the national terror warning level Friday as Homeland Security Secretary Tom Ridge said that an urgent threat had passed. However, the airline industry remained at high alert.
"I know we are all thankful that nothing happened," said Ridge, announcing the lowering of the threat level for most of the country at a news conference.
Ridge acknowledged that certain locations and sectors of the economy, which he did not identify, will keep their security posture at the orange level.
But a U.S. official speaking on condition of anonymity had said earlier that airports and airlines will keep their high alert status.
During heightened alerts, airports are asked to restrict parking near terminals if necessary, increase law enforcement patrols of terminals and perimeters and conduct random checks of vehicles on airport roadways.
The alert level went from orange, signifying a high threat of terrorist attacks, to yellow, signifying an elevated threat. The conclusion of the holidays - and the large gatherings that go with them, played a role in the decision to lower the threat level, Ridge said.
"Although we've returned to yellow, we have not let our guard down," he said. "Yellow still means that we are an elevated risk of attack and we will maintain particular vigilance around some critical resources and locales."
Ridge said he did not know yet whether the orange alert had actually disrupted a planned attack on U.S. soil. Past increases in security measures have served as a deterrent, persuading terrorists to change their targets, said Ridge, citing interviews with prisoners.
In particular, a group of operatives in Turkey decided not to target an American diplomatic building there because security was too tight, Ridge said. In November, they hit a British consulate instead.
"When we raise the security level, when you have more police, when you have frankly more security professionals involved in protecting communities and critical pieces of infrastructure, it is a deterrent. It does disrupt activity," Ridge said.
Homeland Security ranks threats by colors, starting with green at the bottom and followed by blue, yellow, orange and red as perceived dangers intensify. The warning level can be changed for the entire country or for specific regions and economic sectors.
The level was raised to orange, or the second-highest level, on Dec. 21. That marked the fifth time the national alert level was raised to orange since the system was announced in March 2002. It has never dipped below yellow, representing an "elevated" risk.
Ridge said the decision to go to orange was sound. Several streams of intelligence pointed to imminent, simultaneous attacks against U.S. interests, he said.
Some officials have worried that operatives of the al-Qaida terrorist network were deliberately trying to spoof U.S. and international intelligence networks aimed at uncovering terrorist threats, by planting misinformation on lines of communications they believed were monitored.
However, other U.S. officials said the amount and energy level of the threatening intelligence were too widespread for this to entirely be a disinformation campaign.
"Clearly one of the biggest challenges that the intelligence community has, that we have in this country, that we have internationally, is trying to distinguish between information that we should act upon and information that is intentionally designed to deceive us," Ridge said.
He said officials remain fearful about the aviation system, particularly the threat of overseas flights being hijacked and used in Sept. 11, 2001-style attacks on American targets.
Security was raised to extraordinary levels over the last several weeks. In particular, more than a dozen international flights were canceled and military helicopters patrolled during the large celebrations on New Year's Eve in Las Vegas and at Times Square in New York City.
In addition, the Homeland Security Department directed teams of experts to New York, Washington, Las Vegas and Los Angeles, to hunt for signatures of a radiological attack. None was detected.