Some of the flights are the same as those that drew increased attention when the US' terror alert was raised to orange, or high, just before Christmas.

Two officials who spoke on condition of anonymity on Friday stressed there was no specific information about what might be planned, only that those flights are possible targets.

But there are no plans to raise the terror alert because of the latest threats, said Brian Roehrkasse, a spokesman for the Homeland Security Department.

"We remain concerned about al-Qaida's desire to target aviation, especially international aviation," he said.

Intelligence sharing 

"The US intelligence community continues to gather specific credible threat information on international flights, as we have done in an ongoing basis in the past few weeks.

"We have shared this information with our international partners, and will work with them to put in place the appropriate security measures."

Over the holidays, security was tightened considerably around the flights that concerned officials. Passenger airline cargo was inspected, for example, and law enforcement's presence was increased around airports.

"We remain concerned about al-Qaida's desire to target aviation, especially international aviation"

Brian Roehrkasse,
Homeland Security Department

No flights have been delayed or canceled due to the new threats, officials said.

However, a senior law enforcement official said US officials are talking to British and French authorities and no decisions have been made about delaying or canceling future flights.

Flight delays 

Another senior law enforcement official said the intelligence being gathered is similar to what US authorities were hearing during the heightened terror alert in December.

That prompted US officials to ask for the cancellation of two British Airways flights from London to Washington and six Air France flights between Paris and Los Angeles.

A number of other flights were delayed for hours so passengers could be checked against watch lists.

US officials say they believe the process for checking the backgrounds of airline passengers and crews has been improved so that those long delays probably won't be repeated.

An Air France spokeswomen in New York, Diane Cornman, said there was good cooperation among the airline and US and French government officials.

"We have been complying with all security measures," she said.