Bags were painstakingly checked, babies were frisked, and in-flight screens showing a plane's location and flight path had to be switched off.
International airports from South Korea to Paris had ramped up security Monday, causing long queues and inconveniences, after last week's attempted attack aboard a Detroit-bound plane. Airlines managed to keep the disruptions and delays to a minimum, though, by giving many travelers advance warning of the new security measures.
At London's Heathrow Airport, Europe's busiest air hub, small lines built up at departure gates, with flights to the U.S. running about an hour behind schedule. Most passengers, traveling for the holidays, took things in stride.
"It's Christmas as well, so you'd expect some delays," said Mary Lecarpentier, 45, who was flying from London to New York for New Year's celebrations. "I've only just joined this line and it's fine. I'm nearly there."
British Airways was telling customers flying to the U.S. to carry only one item of hand luggage and to expect any gifts they were carrying to be unwrapped at security. Virgin Atlantic posted a similar announcement on its Web site. Both airlines said delays had been minimal.
Officials have given scarce details about the restrictions introduced over the weekend, saying they do not want terrorists to know about potential security measures after a man aboard a Northwest Airlines flight Friday from Nigeria through Amsterdam to Detroit, Michigan, tried unsuccessfully to ignite an explosive as the plane prepared to land.
Measures introduced at airports in Asia led to only minor delays. At Incheon airport, South Korea's main gateway, passengers and baggage were checked repeatedly in the customs, immigration and quarantine areas at the request of U.S. authorities.
Many airports introduced a secondary level of security, after the main security gates, for travelers going to the U.S. At Toronto's Pearson International Airport, the additional measures meant some passengers were made to wait more than three hours to board. Before one Continental Airlines flight leaving Cancun, Mexico, for Newark, New Jersey, even babies were being frisked.
Canada on Monday banned most carry-on luggage for U.S.-bound passengers. Passengers can carry on only medical devices, small purses, cameras, laptop computers, canes, walkers, diaper bags, musical instruments and bags containing "life-sustaining items."
Transport Canada said it is trying to alleviate backlogs at security checkpoints, after passengers complained of chaos and long lines at Pearson over the weekend and Monday morning.
Police are now helping with security at four of Canada's biggest airports after Transport Canada requested assistance.
Many travelers said that, once on board their flights, they were banned from opening overhead bins or visiting the toilets during the last hour of flight. Some passengers said they were asked to remove blankets from their knees, and one woman said a flight attendant had threatened to confiscate Christmas cards she had been writing in her lap.
In-cabin screens normally showing the plane's location and flight path were switched off on an Air France flight Saturday from San Francisco to Paris _ as a "security measure," flight attendants said.
There were minor delays at Paris' Charles de Gaulle International Airport, where officials said security backlogs for flights to the U.S. early Monday had delayed overall traffic by an average of one hour. But by Monday evening, the backlogs had cleared up.
Jason Iglesias, a 30-year-old service industry worker from New York City, said he received an e-mail Monday that urged him to get to his gate as early as possible. He did _ only to breeze through security and languish at the gate for two hours.
Elsewhere in Europe, security measures did not cause significant delays.
Travelers were divided about the effectiveness of new security checks.
Richard Brandt, a 36-year-old resident of Ireland, said it didn't make sense to ban passengers from using the bathroom an hour before the plane landed.
"I can't see what kind of difference that would make. If it's an eight hour flight they could still have seven hours to blow up the plane if that's what they want to do," he said in Poland.
For 24-year-old Sylwia Cieplak, who was returning to Milan from Poland, the attempted Christmas-Day attack only intensified her fear of flying.
"I really hope there will be more security on my flight," she said, rushing outside for a cigarette to help calm her nerves. "They can check everything; that's no problem for me."
Associated Press writers Jamey Keaten and Angela Charlton in Paris, Vanessa Gera in Warsaw, Poland, John Heilprin in Geneva, Harold Heckle in Madrid, Ariel David in Rome, Rob Gillies in Toronto and Matt Moore in Frankfurt contributed to this report.