Three weeks after warning of possible attack on the United States, the government has lowered the terror threat level, saying the danger over the holiday season had passed but airlines were still at risk.
Homeland Security Secretary Tom Ridge announced the reduction in the color-coded threat level to "elevated" or "yellow" from "high" or "orange". But he said airlines, other sectors and some unspecified parts of the country would be asked to remain on a heightened state of alert to guard against possible terror attacks.
"We are still concerned about continued threats, but the threat condition we have been following has diminished," he told a news conference. "With the passing of the holidays and many large gatherings ... we have made the decision to come down to yellow."
The alert level was raised to "orange" - the second highest threat level - on December 21st. At the time Ridge warned of a high risk of an attack around the Christmas and New Year holidays that could be bigger than those of September 11th, 2001.
Since then, US authorities have passed on intelligence regarding specific threats to airlines, prompting carriers in Britain, France and Mexico to cancel several flights.
The United States also ordered foreign airlines to put armed marshals on some flights and dispatched fighter jets to escort some incoming planes.
The five-level color-coded scheme, established to help Americans better prepare for future attacks, has generally held steady at "yellow" but has been raised to "orange" five times since it was created in March 2002.
Mr Ridge said the heightened alert helped over the busy holiday season. "The potential danger that large gatherings present during the holidays has passed," he said. "They passed safely and without incident."
He said: "We know from experience that the increased security and vigilance that accompanies a rise in the threat level does make a difference in deterring and disrupting a terrorist attack." he said.
Mr Ridge said the government knew in part from interrogating detainees that plans for another attack have been disrupted.
"One of the most persistent and consistent reports we have from multiple sources (is) the continued interest by al Qaeda ... to use aircraft, but particularly commercial aircraft," he said.