We're heading into the peak travel season in the US with unprecedented security measures at scores of airports around the nation -- including the Minneapolis-St. Paul International Airport.
Here's a look at some of the issues involving the enhanced air travel security in place.
Q: What exactly is the enhanced security that travelers can expect?
A: So-called full body scanners have been in place since 2007 on an experimental basis. The first of them arrived this spring at Minnesota's main airport, and now there are a half dozen of them at three of the security gates at Terminal 1, formerly known as the Lindberg Terminal.
The other gates are using conventional magnetometer equipment and hand searches. All the gates have retained the traditional X-ray luggage machines and Transportation Security Administration personnel.
Recently the TSA has instituted so called "enhanced" manual searches that involve potential contact with a woman's breasts or the genital areas of men and women. The practice is meeting with some resistance but is not routine for travelers passing through security checkpoints.
Q: What changed? Why is this happening now?
A: Two factors have driven this change. One was the Christmas Day plot, in which Umar Farouk Abdulmutallab tried to bring down a Northwest Airlines flight with plastic explosives hidden in his underwear.
The other was routine audits by both the Government Accountability Office and the TSA's own Inspector General. They found that decoys sent through security were routinely smuggling concealed items through security.
The TSA determined more thorough pat downs would have better blocked those breaches. The agency started testing an "enhanced" pat down in Las Vegas and Boston in August and rolled it out nationwide -- mostly unannounced -- as of the beginning of November.
Q: What will get travelers sent through a scanner or patted down?
A: For now, the scans and pat downs are secondary in Minnesota. Travelers who set off a metal detector may be sent for additional examination in a full-body scanner, which uses either low-power X-rays or microwaves.
Travelers who object to the technology may "opt out" and be subjected to a manual search, either at the security checkpoint or in a private area.
Security officials are also selecting a small number of passengers at random for the scans. The results of the scan may prompt further examination, such as a pat down. People who decline either a scan or a pat down will be refused passage to their flight.
Q: How does the TSA decide who should be scanned or patted down?
A: Eventually, the scans are expected to be mandatory and all travelers will be subject to one or the other and in some cases, both.
For now, which may be a matter of choice. People with metal implants in their bodies may set off airport magnetometers and be subject to further examinations. Many choose the electronic scans, in lieu of a physical examination. Others choose to bypass the scanners and accept a physical examination.
For others, scanners simply aren't available. There are only about 400 scanners nationwide, and they're only in about 70 of the 453 airports. The TSA is expecting to have 1,000 of the machines in place by the end of next year, so as time goes on, more and more people will be subject to full body scans.
Security officials also use the scanners on a case-by-cases basis. TSA adminstrator John Pistole says his agency won't divulge its criteria for selecting search subjects publicly, to prevent would-be terrorists from skirting the system.
But the TSA says just 3 percent of travelers are subject to intrusive pat-downs.
Q: What's all the fuss about? Why is there so much controversy?
A: Several factors have combined to raise this issue on the public agenda. One is simply more travelers. Travel is up and more people are being exposed to the new security. Traffic this year is expected to be about 5 percent higher than last year at Minneapolis-St. Paul International Airport. More people are simply experiencing the new systems.
The secrecy of the TSA's search methods have also raised questions. Some have accused security officials of separating out attractive women for full-body electronic scans, for the suspected titilation of the security personnel observing the scanner displays.
Others have raised suspicions of racial or religious profiling amongst airline passengers. Yet others say the discomfiting pat-downs are actually retaliation for travelers who won't cooperate with electronic full-body scans.
And despite assurances that the scanned images are never retained, 35,000 images -- paired with conventional video images of the same people --- were saved in a millimeter wave machine at a federal courthouse in Orlando Florida. That was a different federal agency and different machines. But the incident has raised doubts about whether the government is actually living up to its promises that potentially embarrassing images will never be retained.
Others have questioned the legal or constitutional basis for the search, and accused the federal government of providing TSA personnel legal immunity for searches, potentially permitting misconduct during searches.
Lastly, pilots and other fliers who regularly go through the machines have raised health questions about the low-energy X-rays and radio frequency emissions from the scanners.
The TSA has offered point-by-point rebuttals of each of those objections, saying the process is legal, fair, efficient, necessary and safe. The agency has also posted video recordings of controversial incidents, like a confrontation with a woman in Florida and the removal of a boy's shirt in Utah, offering explanations for some of the highest-profile incidents.
Q: Are there religious exemptions for the searches?
A: The TSA says no, that the security is standard for everyone who intends to board an airliner subject to US jurisdiction. There have been some charges that Muslim women wearing religious garb would be exempt from scans or pat downs, or would be allowed to pat themselves down.
TSA administrator John Pistole says that isn't true, although he did say people with religious headcoverings would be allowed to pat down their own headwear, provided they agreed to subject their hands to chemical explosive screening immediately afterward.
Q: What's the best strategy for dealing with the heightened security?
A: That depends on your point of view.
If your goal is to efficiently pass through the system, security officials say you should arrive early to allow for a delay at the security checkpoint. They suggest removing everything from your pockets, as well as any jewelry or metallic accessories -- and to avoid clothing with any more than minimal metallic components, like a zipper. At the checkpoints this week, nearly everyone successfully passing through a metal detector appeared to proceed directly to their flight after retrieving their belongings from a standard luggage X-ray examination. Compliance with standard TSA regulations on liquids and aerosols will also avoid delay.
You can also check the TSA website, which lists security checkpoint wait times at www.tsa.gov/mobile. The wait times are listed by checkpoint, but are only reports from other travelers. The TSA does not track or verify the information independently.
Libertarians and some health advocates have said that the better option is mass civil disobedience that would prompt a breakdown of the security and aviation systems and force the federal government to retreat from its advanced imaging efforts.