Despite tough talk on the Internet, there was little if any indication of a passenger revolt at many major U.S. airports, with very few people declining the X-ray scan that can peer through their clothes. Those who refuse the machines are subject to a pat-down search that includes the crotch and chest.
Many travelers said that the scans and the pat-down were not much of an inconvenience, and that the stepped-up measures made them feel safer and were, in any case, unavoidable.
"Whatever keeps the country safe, I just don't have a problem with," Leah Martin, 50, of Houston, said as she waited Monday to go through security at the Atlanta airport.
At New York's LaGuardia Airport early Tuesday, Jeannine St. Amand got a pat-down in front of her husband and two children. The 45-year-old from Fredericton, New Brunswick, Canada, figured she got one because the underwire of her bra tripped the metal detector.
"It's hard to remember all the restrictions. Next time, I'll wear a different bra," she said.
She opted to have the pat-down in public rather than private and said it was professional and done by a female agent.
"She tells you ahead of time what she is going to do, which is a good thing because that could be awkward," St. Amand said.
Transportation Security Administration chief John Pistole pleaded with Thanksgiving travelers for understanding and urged them not to boycott full-body scans on Wednesday. It would only snarl what is already one of the busiest, most stressful flying days of the and would only "tie up people who want to go home and see their loved ones," he said.
"We all wish we lived in a world where security procedures at airports weren't necessary," he said, "but that just isn't the case."
He noted the alleged attempt by a Nigerian with explosives in his underwear to bring down a plane over Detroit last Christmas.
About two-thirds of Americans support using the full-body scanners to increase security, according to a Washington Post-ABC News poll published Tuesday. But half of the 514 adults surveyed by phone said the more rigorous pat-downs go too far.
At Chicago's O'Hare Airport, Gehno Sanchez, a 38-year-old from San Francisco who works in marketing, said he doesn't mind the full-body scans. "I mean, they may make you feel like a criminal for a minute, but I'd rather do that than someone touching me," he said.
A loosely organized Internet campaign is urging people to refuse the scans on Wednesday in what is being called National Opt-Out Day. The extra time needed to pat down people could cause a cascade of delays at dozens of major airports, including those in New York, Los Angeles, Chicago and Atlanta.
"Just one or two recalcitrant passengers at an airport is all it takes to cause huge delays," said Paul Ruden, a spokesman for the American Society of Travel Agents, which has warned its more than 8,000 members about delays. "It doesn't take much to mess things up anyway."
Most who don't like the screenings just grumble but don't really cause a big fuss, at least not that Cris Soulia, a TSA officer in San Diego and president of a local union, has heard or seen.
"We're not here groping people. We're not here molesting people. We're checking them for items and explosives. And yes, explosives can be hidden in the groin area," she said.
More than 400 imaging units are being used at about 70 airports. Since the new procedures began Nov. 1, 34 million travelers have gone through checkpoints and less than 3 percent are patted down, according to the TSA.
At the White House, press secretary Robert Gibbs said the government is "desperately" trying to balance security and privacy and will take the public's concerns and complaints into account as it evaluates the new, more stringent boarding checks.
The American Civil Liberties Union has received more than 600 complaints over three weeks from passengers who say they were subjected to humiliating pat-downs at U.S. airports, and the pace is accelerating, according to ACLU legislative counsel Christopher Calabrese.
"It really drives home how invasive it is and unhappy they are," he said.
Ricky D. McCoy, a TSA screener and president of a union local in Illinois and Wisconsin, said the atmosphere has changed in the past two weeks for officers in his region. Since word of the pat-downs hit the headlines, officers have been punched, pushed or shoved six times after they explained what would be happening, McCoy said.
"We have major problems because basically TSA never educated the public on what was going on," he said. "Our agency pretty much just threw the new search techniques out there."
Stories of alleged heavy-handed treatment by TSA agents captured people's imagination.
A bladder cancer survivor from Michigan who wears a bag that collects his urine said its contents spilled on his clothing after a security agent at a Detroit airport patted him down roughly.
Tom Sawyer, a 61-year-old retired special education teacher, said the Nov. 7 experience left him in tears. "I was absolutely humiliated. I couldn't even speak," he told MSNBC.com.
During an appearance on CBS, the TSA's Pistole expressed "great concern over anybody who feels like they have not been treated properly or had something embarrassing" happen.
A video showing a shirtless young boy resisting a pat-down at Salt Lake City's airport has become a YouTube sensation and led to demands for an investigation from Rep. Jason Chaffetz, R-Utah, an outspoken critic of TSA screening methods. The video of the unidentified boy was shot Friday by a bystander with a cell phone.
The TSA said in a blog posting that nobody has to disrobe at an airport checkpoint apart from removing shoes and jackets. According to the TSA, the boy was being searched because he triggered an alarm inside a metal detector, and his father removed the youngster's shirt to speed up the screening.
The boycott campaign was launched Nov. 8 by Brian Sodergren, who lives in Ashburn, Va., and works in the health care industry.
"I just don't think the government has the right to look under people's clothes with no reasonable cause, no suspicion other than purchasing a plane ticket," he said in an interview with The Associated Press.
Associated Press writers Eileen Sullivan, Julie Pace, Sarah Brumfield and Joan Lowy in Washington; Russell Contreras in Boston; Dan Elliott in Denver; Emily Fredrix and Karen Matthews in New York; and Sophia Tareen in Chicago also contributed to this report.