CBS News National Security Correspondent David Martin reports the cancellations were the result of late-night work by American officials to convince their French counterparts that the planes might be used by terrorists.
The U.S. has intelligence information that at least one of the cancelled Air France Paris-to-Los Angeles flights might have been commandeered by al Qaeda and used in a terror attack against the United States.
The U.S. Embassy in Paris asked the government to cancel the Air France flights "for security reasons," a ministry spokesman said.
Three of the flights were scheduled to depart Wednesday — two from Paris and one from Los Angeles. Air France gave the flight numbers as 68, 69 and 70.
The three other flights were scheduled to leave on Christmas Day; two from Los Angeles and one from Paris. Air France listed those flight numbers as 68, 69 and 71.
Air France said it was working to arrange accommodations for stranded passengers.
The U.S. Department of Homeland Security had been meeting with officials from the French government in recent days over concerns about a possible terrorist attack, a spokesman for the Transportation Security Administration said Wednesday.
Homeland Security Secretary Tom Ridge has personally been involved in the briefings with the French officials, as well as officials from other nations, TSA spokesman Brian Doyle said.
Doyle refused to name other countries that had been contacted.
"We're talking to our counterparts in other countries about security concerns," Doyle said.
The cancellations come aid heightened security and a high terror alert in the United States after intelligence agencies reported intercepting hints of an imminent terrorist attack. Federal officials fear that al Qaeda could use foreign planes to strike U.S. targets.
However, officials said the intelligence painted a confusing picture about where, when and how the terrorists might strike.
Possible targets range from the headquarters of the U.S fleet in the Persian Gulf in Bahrain, to Reagan National Airport in Washington, to Port of Valdez, Alaska — a major petroleum center. The mode of attack could be a hijacked commercial airliner or a so-called "dirty" radiological bomb. And the threat seems to apply to a period running to the end of January.
One official cautioned that most of the reported threats were uncorroborated — some were from only a single informant or communications intercept — and may be unconnected to a larger al Qaeda plot.
Despite the unclear direction of the threats, they were deemed credible because both British and U.S. intelligence heard similar threats at the same time. The volume and nature of the threats prompted the move to orange or "high" alert on Sunday, triggering extraordinary security around the nation.
Local officials boosted security at many potential targets, including the Port of Valdez, where armed Coast Guard patrol boats were more visible and ship boardings were on the increase.
The Pentagon is increasing air patrols over major cities and critical installations like dams and power plants.
The military deployed surface-to-air missile systems in the Washington area and was considering locating more anti-aircraft systems in the New York City region, a defense official said, speaking on condition of anonymity.
The warning from the Homeland Security Department on Sunday about a possible al Qaeda attack this holiday season was focused mainly on the threat from foreign commercial airliners, according to U.S. officials.
But some of the measures are focused on the vulnerability of cargo planes. On Tuesday, the Transportation Security Administration said it had increased inspections of cargo companies to ensure compliance with tighter rules enacted last month.
A TSA spokesman said extra law enforcement added to the perimeters of airports in the past three days was specifically put in place to fortify air cargo facilities.
Also Tuesday, new evidence emerged that terrorists may be planning attacks at Western targets in Turkey during the holidays, according to a police document, while Americans and Britons living abroad were warned to keep a low profile.
Britain's top police officer warned people to be vigilant during the holiday season and in Yemen, security around embassies was noticeably tighter.
The most chilling warning came in Turkey, where an internal police intelligence document obtained by The Associated Press on Tuesday cautioned that militants were infiltrating the country to complete preparations for new attacks against Western targets as well as Istanbul's popular Akmerkez shopping mall.
Militants believed to be linked to al Qaeda bombed two Istanbul synagogues in mid-November and later struck the British consulate and the local branch of a London-based bank. Those attacks killed 62 people, including the suicide bombers.
"It is being detected that the preparations for a large-scale third wave of attacks to follow up the suicide bombings has been completed," said the document, which was signed by two senior police officials, including the head of the Istanbul security department.
Westerners were keeping a low profile Wednesday in the Saudi capital of Riyadh.
"Everybody is aware that there is a terrorist threat and Christmas time would be a more active period for the terrorists to do something," said Richard May, manager of the Seder Village compound in Riyadh, which has been named by the U.S. and British embassies as a possible target.
In Bahrain, the U.S. Embassy in Manama warned that it had received information about a possible terrorist attack during the holidays and cautioned Americans to avoid places where Westerners gather and to reduce unnecessary travel.
The Persian Gulf country is home to the U.S. Navy's Fifth Fleet. More than 5,000 Americans live there.
In the past 13 months, al Qaeda-linked groups have staged major terror attacks in Saudi Arabia, Kenya and Turkey. Yemen was the site of the 2000 bombing of the USS Cole in Aden harbor, which killed 17 U.S. sailors.