Security fears amid a heightened terror alert also prompted a two-day suspension of oil shipments from Alaska's major port of Valdez, Coast Guard and Department of Homeland Security officials said. The halt of transfers of oil onto tankers began on Tuesday and was lifted on Thursday.

An Aeromexico flight to Los Angeles from Mexico City was canceled on New Year's Eve and Jan. 1 because of suspicions would-be hijackers might have booked tickets, Mexican and US officials said.

British Airways canceled one of its three daily flights from London to Washington following security advice from the government, an airline spokesman said. The return flight was also scrapped.

The day before, passengers aboard the same inbound flight, BA 223, were held on the tarmac at Washington's Dulles International Airport for several hours of questioning but no arrests were made.

The oil suspension in Alaska was part of "a continuing effort to ensure the security of our homeland," consistent with Code Orange, the heightened alert level in effect since Dec. 21, said Russ Knocke, a Department of Homeland Security spokesman.

It was not clear what specifically triggered the decision to suspend the traffic.

Valdez is the terminal for the trans-Alaskan pipeline from Prudhoe Bay. The 800-mile pipeline normally carries about 1 million barrels a day to Valdez, or about 17 percent of US domestic production.

A Bush administration official said US intelligence remained particularly concerned about "credible" threats to Los Angeles-bound flights from Paris and Mexico City.

In boosting the alert level last month, Homeland Security Secretary Tom Ridge said Osama bin Laden's al-Qaeda movement appeared intent on matching or outdoing the Sept. 11, 2001, hijacked airliner attacks that killed nearly 3,000 people.