WASHINGTON — U.S. concerns about terrorist plots to hijack overseas flights headed for the United States remained intense on Christmas Day, officials said, even as French authorities reported that they had found no evidence that Al Qaeda operatives had planned to commandeer an Air France jetliner headed for Los Angeles.
U.S. intelligence officials said they continued to receive current and credible intelligence indicating that such an attack could be in the works -- possibly a series of coordinated hijackings -- and that Al Qaeda operatives could be targeting any number of overseas cities from which to launch such operations.
Some of the information -- much of it gleaned from electronic intercepts and human sources -- indicates that terrorists are interested in using commercial or cargo jetliners as guided missiles in an assault on urban areas, symbolic targets or parts of the critical infrastructure of the United States, including nuclear plants and petroleum facilities, said several U.S. officials interviewed Thursday.
"This is a broad and serious threat that is not going to disappear with the cancellation of one or two flights," said one U.S. official who, like others, spoke on the condition of anonymity.
"There is a lot of crisscrossing [intelligence] data that points to certain flights, certain times and certain countries," the official added. "It's not just in one location, point of departure or arrival. It's not only France and it's not only L.A."
Officials said they were particularly concerned about what appeared to be incomplete information coming out of France about the fate of several men whose names had appeared on the passenger manifest of an Air France flight from Paris to Los Angeles early Christmas Eve.
The men were scheduled to board Flight 68, which was one of six canceled Wednesday at the urgent request of the U.S. and French governments, based on what U.S. intelligence officials said were multiple and credible indications that they may have been targeted for attack. Air France announced flights would resume today.
The Los Angeles Times reported Wednesday that U.S. officials had told French authorities that as many as half a dozen passengers on Flight 68 might be Al Qaeda or Taliban terrorists, and that one of them was a trained pilot with a commercial license.
On Thursday, French authorities said that they searched and questioned at least seven passengers who had checked in for Flight 68 at Charles de Gaulle Airport, and that they made no arrests and did not open a judicial inquiry.
"Some people were interrogated and their baggage was searched. But they are free," said a French official, who asked to remain anonymous. "Nothing in particular was found. No terrorists were identified. There is nothing new today and no problems."
But one U.S. official said Thursday that at least some of the men whose names had been given to the French never showed up at the airport -- including the man believed to be a pilot -- and that he did not believe French authorities had questioned them.
"We haven't heard the full story," said one U.S. official, particularly the details about how many of the men identified by U.S. intelligence were questioned by French authorities, and what they said before being let go.
More information surfaced Thursday about why U.S. officials were so fearful that the Air France flights might be targeted for hijacking.
One U.S. official, citing electronic intercepts, said terrorist operatives had been overheard discussing specific flight numbers and airlines without mentioning a specific day, while other conversations alluded to attacks on the Christmas holiday "and other days."
"It was not just coincidence of names," the official said. "There were other indicators that raised concerns."
For their part, French authorities said they took the U.S. request very seriously. After a flurry of high-level conversations between the two governments Wednesday, the office of the prime minister announced the cancellations based on information relayed by the U.S. Embassy in Paris about a plot to commandeer a Paris-Los Angeles flight for a Sept. 11-style attack.
"This decision to cancel the flights was taken at the highest level," a senior French law enforcement official said. "But this was all based on information coming from the Americans. And apparently nothing was found."
Those singled out for questioning at the airport Wednesday included citizens of the United States, France and Belgium, the French interior ministry official said. He did not say whether the passengers under scrutiny had Arab names and did not give the precise number of those questioned.
But French media reported Thursday that police questioned two men of Arab origin who turned out to be a diplomat and an athlete.
French media also reported that U.S. law enforcement provided French counterparts with the name of a Tunisian with a pilot's license as a potential suspect.