Similar threats surfaced just before the holidays and were a primary reason the Department of Homeland Security raised the nation's terror threat level to Orange on Dec. 21.
At least six foreign flights from Paris, London and Mexico City were cancelled and a dozen others were delayed from Christmas Eve through the first week of January. Then the level of alarm subsided and the threat level was lowered.
Now, U.S. security officials say the threat has re-emerged and authorities have been meeting throughout the day to consider increased security measures including additional air marshals, military escorts of inbound jets and even possible flight cancellations.
At the same time, officials with the Department of Homeland Security say they have no plans at this time to raise the terror threat level again. But, the level of concern is rising and aviation again appears to top the worry list.
There are no plans to raise the terror alert because of the latest threats, Homeland Security Department spokesman Brian Roehrkasse said.
"We remain concerned about al Qaeda's desire to target aviation, especially international aviation," he said. "The U.S. 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."
No flights have been delayed or canceled due to the new threats, officials said. However, a senior law enforcement official said U.S. officials are talking to British and French authorities and no decisions have been made about delaying or canceling future flights.