Facing another week of uncertainty over the terrorist threat from the air, international airlines and foreign governments are greeting increased security with a combination of skepticism and support as flight cancellations and delays spread.
"The decision to operate next Monday's flight to Riyadh (Saudi Arabia) will be kept under review throughout the weekend," British Airways says on its Web site.
Airlines have canceled seven flights since Wednesday, with Mexico City and London the points of origin and Los Angeles, Washington Dulles International Airport and Riyadh, the destinations. Dulles was the takeoff point for the hijacked flight that destroyed part of the Pentagon in the Sept. 11, 2001, attacks.
South Korea's national police agency responded sympathetically to American requests for international cooperation, saying it would deploy armed officers on individual U.S.-bound flights if warranted based on information about a terrorist threat to any specific flight.
Aeromexico canceled two flights from Mexico City to Los Angeles because of U.S. security concerns and a third turned around after takeoff because Mexico thought the airline hadn't screened passengers properly.
Authorities on the ground "said that we didn't search coats and sweaters worn by customers," said Fernando Ceballos, Aeromexico's assistant director of airports. "We didn't agree with that, but we ordered the plane back anyway."
In France, a police official said six cases of mistaken identity were behind the pre-Christmas grounding of six Air France flights between Paris and Los Angeles over terrorism fears. The names of six passengers sounded similar to those of terrorist suspects provided by the FBI, prompting the French government to ground the planes, the official said.
Watch lists that investigators use have phonetic spelling of Arab names, a senior FBI official said, making mistakes inevitable because individuals will have similar names.
Mistakes are inevitable, but the failure to respond "is a far worse alternative in spite of the inconvenience to passengers," said Sen. Jay Rockefeller of West Virginia, senior Democrat on the Senate Intelligence Committee.
Pierre Debue, director of the French border police, said U.S. officials have asked France to check out a few suspicious names on passenger lists nearly every day since Christmas Eve.
One turned out to be a 5-year-old child, and another was a prominent Egyptian scientist, he said.
Rockefeller said all the activity in the international air traffic system is being driven by "very specific" intelligence derived from "an enormous amount of much more than single-source reporting." He said the information can come from computerized watch lists, interception of communications and intelligence agents.
British Airways said a flight to Riyadh, which had been due to leave London's Heathrow Airport on Saturday, was scrubbed along with a return flight scheduled to leave Riyadh on Sunday.
The airline also canceled its third flight in 24 hours Friday between London and Washington's Dulles International Airport, and another flight from London arrived at Dulles two hours late Friday because of additional passenger screening.
Under an agreement reached with the United States, Mexico began sending armed security agents last week on some flights to the United States. Mexico also is in talks with Canada about putting guards on board flights to that country.
Asa Hutchinson, undersecretary for border and transportation security in the Homeland Security Department, pleaded for perspective.
"There's thousands and thousands of international flights every day," he said, and "really, only a small handful were canceled."