The day after Umar Farouk Abdulmutallab’s Christmas Day attempt to set off an explosive device on Northwest Airlines Flight 253, Department of Homeland Security Secretary Janet Napolitano said any additional security measures the agency planned to implement were “designed to be unpredictable.”

Napolitano was referring to added security measures for people flying from international destinations to the United States. Different airlines reported different potential restrictions stemming from these measures, including limiting fliers to one carry-on, or preventing passengers from either holding personal items in their laps or roaming the cabin during the last hour of the flight. Further, guidelines later posted by the Transportation Security Administration (TSA) broadened Napolitano’s statement to include domestic airports. The rules reiterated that “passengers should not expect to see the same thing at every airport.”

Well, the TSA was right about that. Post-Christmas fliers could not have predicted what was in store.

Frequent business traveler Ken Walker flew out of St. Louis on December 27. “I felt pretty sure the new rules would bite me, but they didn't,” he says. “There was nothing new in the security line at the airport, nothing new to see or do on the plane. We left on time, arrived on time, bags dropped on time, no issues.”

Also on the 27th tour guide Ann Lombardi of The Trip Chicks flew out of Atlanta where “TSA agents were patting down everyone from grandmas to first graders. It took two hours to go through the TSA line vs. the normal ten to twenty minutes.”

Further reports from domestic fliers seemed to mimic Walker’s “business as usual” experience. A friend of mine tempted fate on Dec. 30 by flying with a cat, a banjo, and some home-brewed ginger beer, but encountered no delays or unusual security screening while waiting to fly out of Long Beach. Another flier I know reported on New Year’s Eve that “Terminal 4 at JFK is quiet. Increased security presence visible throughout terminal, but check-in plus security took less than half hour. No unusual requests.”

Another friend flying from Austin to Newark on January 3 said “security was the same as pre-Christmas, nothing on board was different,” leaving Newark less than an hour before a stranger strolled into a “sterile area” in Terminal C, resulting in hours of passenger re-screenings and flight delays.

A new TSA security measure went into effect on January 4: “enhanced screening” – full-body frisking and aggressive luggage checks – for anyone flying into the U.S. who originated from or traveled through at least one of 14 nationsdeemed sponsors of terrorism or “countries of interest.” Though Great Britain falls into neither category, a New-York based flier I know, J.T., traveled from Heathrow to JFK on the 4th and got a taste of this enhanced screening.

Soon after checking her suitcase at Heathrow’s British Airways Terminal 5, J.T. encountered a clerk who checked her boarding pass and directed her to stuff her purse into her carry-on, where she had previously stuck her laptop (her alternative was to check it). After that she moved on to the security line where she had to unpack her overstuffed bag. When she was done she "walked away with three separate pieces of luggage again. I wasn't sure why I had to do all the stuffing for those 25 feet, between the clerk checking our boarding passes and the security lines,” J.T. says. When she arrived at her gate, she joined two lines that had already formed – one for females, one for males, and security “opened our bags, went through all compartments, pockets, and cosmetic bags. Then they thoroughly frisked us, body part by body part.” The personnel doing the screening were polite and repeatedly pointed out that they were enforcing U.S. homeland security rules. Beyond being told to stay seated for the final 20 minutes of the flight, J.T. detected no new rules on board. By comparison, between Christmas and the 4th she flew round-trip from London to Belgrade and experienced no new security measures.

While much about airport and airline security procedures will remain unpredictable from day-to-day, here are a few things you can expect.

Expect to provide airlines with more information.

President Obama noted on Jan. 5 that the U.S. intelligence community failed to “connect those dots” that would have placed Abdulmutallab on the government’s “no fly” list. Since Christmas, counterterrorism officials have added more names to that list, and to ensure yours isn’t one of them, the TSA’s Secure Flight program requires you to tell the airlines your name as it appears on your government-issued I.D. as well as your date of birth and gender. The airline will then transmit your information to the Secure Flight system, which compares your name to names on government watch lists. A match would place you either on the “no fly” list or a Selectee List making you eligible for enhanced screening. Secure Flight is being phased in airline-by-airline with full implementation by domestic airlines expected by early 2010 and by international airlines by the end of the year.

Expect the possibility of behavior detection.

Current TSA guidelines note that the agency has the “ability to quickly implement” additional screening measures as needed, including “behavior detection.” While the TSA is not explicit about what that detection would entail, the possibility invites a comparison to the psychological questioning used by the Israeli Security Agency.

Travelers who arrive at Tel Aviv’s Ben Gurion airport encounter security personnel famous for asking such garden-variety questions as “How are you?” or “What museums did you go to?” The point isn’t what you answer but how you act when you do. While the questioning itself can cause distress, Israeli security is trained to know the difference between their making you nervous versus your being nervous for more sinister reasons.

Most travelers appreciate the point of the interviews, though some find them excessive. Trudy Swafford, questioned at Ben Gurion by security in 2004, notes on airport review site Skytrax that “I understand their concerns but the questions [they] ask a tourist are downright stupid. My 20-year old daughter and myself were asked repeatedly about our ‘relationship’ to each other. Is there something unusual about a mom and daughter with the same last name? We were asked what was the name of our taxi driver. Sorry, I didn't ask his name, just his price.” Despite these objections as well as detractors who say such interviews amount to profiling, Ben Gurion has not had a security breach since 2002.

Expect even more comparisons to how other nations secure their airports.

Lombardi recalls being pulled out of the pre-departure security line at Zurich’s Kloten Airport about a year ago, when an inspector examining her carry-on found a pocket knife tucked in hiking boots she hadn’t used in years. “I had totally forgotten about the knife. Then he asked me if I would like the knife sent to my home address --I'd need to pay the postage. I was struck by the civil, low-key, professional way in which this incident was handled.”

Lombardi adds that “In Switzerland, I have routinely seen select passengers -- often from countries known for "terrorist camps"-- discreetly taken out of line for more thorough screening. No one seems to complain or protest. These procedures are considered a regular part of airline screening. There is no worry about ‘political correctness’ or ‘racial bias.’ I remember hearing my Swiss friend say, ‘it makes perfect sense to concentrate our resources on screening travelers fitting a certain profile rather than 85-year-old American grandmothers from London or Los Angeles.’"

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