Just in time for the busiest travel period of the year, critics opposed to the government's new regimen of full-body scans and intrusive pat-downs have dubbed the day before Thanksgiving National Opt-Out Day. Still others are urging travelers to boycott flying altogether.

But does the newest "new normal" of air-travel security in the post-9/11 world deserve such attention or as much media coverage as it has received? And do any of the partisans on either side really care whether you're fully informed about the issues?

Rather than cast my frequent-flying lot with one side or the other, allow me to offer some facts about the situation and answer some of the larger questions as objectively and fairly as possible.

Unlike too many of the partisans in the debate, I trust your judgment to make the right call for your personal travel needs.

How'd We Get Here?

The current outrage against the Transportation Security Administration is in stark contrast to the overwhelming demand for federalization of airline security after terrorists hijacked four airliners on September 11, 2001. The bill that created the TSA passed unanimously in the Senate and without objection in the House of Representatives. President George W. Bush signed the Aviation and Transportation Security Act on November 19, 2001.

Before the TSA, security rested with the airlines, and they farmed the job out to private firms. The track record of the rent-a-cops was atrocious: Private screeners missed all manner of weapons and other contraband. Over the years, a small number were revealed to have criminal records or be illegal aliens. The turnover of the workforce averaged 126 percent annually. It was 200 percent at Boston's Logan Airport, where two of the aircraft were hijacked on 9/11.

Contrary to popular belief, however, commercial airports are not required to use government screeners. The 2001 legislation allows airports to operate with private firms. Just 16 of the nation's 450 or so commercial airports have gone that route. Orlando's lightly used second airport, in Sanford, Florida, announced last week that it would go private.

Also worth noting: Although high-profile critics like Representative Ron Paul claim the government should be out of the airport-security business because it is a task best left to private industry, the nation's carriers were among the biggest proponents of federalizing the task. No carrier has ever asked for the responsibility back, either. And most Americans continue to believe that airport security is a government duty, much as seaports and navigable waters are handled by the U.S. Coast Guard.

How Has the TSA Performed?

The TSA can claim statistical success: No U.S. aircraft has been successfully attacked since it took over security. And no matter what more sophisticated analysts believe, the public has always judged aviation security by the numbers: No incidents means the system is "safe."

TSA critics claim other post-9/11 security improvements deserve the credit, however. They point specifically to the reinforcement of cockpit doors (and the order requiring doors to remain locked during flight) and new rules that permit pilots to carry firearms in the cockpit. The critics also insist that flight attendant and passenger awareness have foiled the most serious post-9/11 incidents, including the "shoe bomber" Richard Reid and last Christmas' attack by "underwear bomber" Umar Farouk Abdulmutallab.

The TSA's track record for catching contraband at security checkpoints isn't appreciably better than private screeners. But until the current controversy, most criticism has been levied at the TSA's data-mining and watch-list tactics. Several TSA programs to identify potential security threats via information collected before departure collapsed because the agency was unable to keep data private or misused it.

Why Does Security Work That Way?

Some procedures in effect at U.S. airport-security checkpoints date back to the 1960s, when the major threat was hijackers intent on diverting aircraft to Cuba. As threats morphed over the next 40 years, security screening became more involved and intrusive. The adjustments were almost always reactive. Officials introduced methods to stop a future incident that would be patterned on the previous attack.

After 9/11, for example, many more items were prohibited from aircraft because the hijackers' suspected weapons of choice, box cutters, had not been previously banned. Passengers were required to remove footwear for scanning after the December, 2001, shoe-bomb attempt. Most liquids were banned, and carry-on toiletries were required to meet so-called 3-1-1 rules in 2006, after British authorities claimed they foiled a plot to detonate liquid explosives aboard transatlantic flights.

Why Use Full-Body Imagers?

The full-body image scanners and pat-downs are not a reaction to last year's "underwear" bombing attmept, however. In fact, a recent report by the Government Accountability Office questions whether the scanners would have detected the weapon in Abdulmutallab's pants.

The new scanners are just one of a series of devices the TSA has tested and deployed to augment the traditional X-ray machines. Most have quietly disappeared after proving too expensive or no more effective than existing technology. That includes the much-heralded "puffer" machines that shot air at passengers' clothing at they passed through security.

One point to keep in mind: The scanners may be coming on line now, but have been in the works for years and were first approved during the last Bush administration. Michael Chertoff, President Bush's then-Homeland Security secretary, is now a lobbyist for one of the device's manufacturers.

Originally conceived as a secondary screening method, the imaging devices were given top priority by the Obama Administration after the 2009 Christmas incident. Both Homeland Security Secretary Janet Napolitano and TSA Adminstrator John Pistole have endorsed and defended them.

What and Where Are Full-Body Scanners?

The full-body imaging devices actually consist of two separate systems: "backscatter" and "millimeter wave" scanners. Machines of these types were first deployed in 2007 at Amsterdam's Schiphol Airport. A plan to place them at all Italian airports and train stations was abandoned two months ago because Italian security officials concluded they were "slow and ineffective."

The TSA expects 500 of the machines in place by the end of the year, another 500 by the end of 2011, and 1,800 in use at airports by 2014. That's nearly double the number of machines originally envisioned and some of the devices were purchased with funds allocated by the 2009 stimulus bill.

The TSA has been installing full-body scanners since late 2007. As of November 22, the TSA website says 385 machines are in place at 68 airports. Your chances of actually confronting the machines? According to TSA officials, it's about one in three. But it could be as high as 90 percent if you fly from the nation's busiest airports.

How Does the System Work?

When you approach the security-screening checkpoint, you may be able to avoid the full-body imagers simply by tarrying or fussing with your carry-ons. Since virtually all airport checkpoints with full-body scanners continue to have traditional X-ray machines too, assignment to one or the other system is random.

If you refuse a full-body scan, the TSA has the right to give you the new pat-down regime instead. You have the right to insist that it is done by a screener of the same sex, and you have the right to request the procedure occur in a private room. You also have the right to have a traveling companion present during the pat-down.

Keep reading to find out why some flyers dislike the scanners, what triggers a pat-down, and whether Americans are really opposed to the TSA's methods.