Nov. 27--With the most frenetic air-travel period of the year drawing to a close tonight, waiting time in airport security lines should start getting back to normal this week.
But normal doesn't necessarily mean smooth or predictable.
At Logan International Airport in Boston, wait times have dropped steadily since tougher security measures were first imposed after the Sept. 11, 2001, terrorist attacks thanks to better training of staff and passengers.
More than 93 percent of the time this autumn, according to a Globe review of Transportation Security Administration records since early September, Logan passengers waited fewer than 10 minutes to get through security checkpoints.
However, backups have periodically surged to as long as 39 minutes. And for travelers trying to plan how to get through Logan without missing a flight, the bad news is that there have been few clear patterns to when and how long delays form.
Outside of several delays on Monday mornings, when business travelers are pouring into Logan, and virtually no big delays after 6 p.m., long waits can develop at all times of day and at all five terminals.
Frequent business travelers -- who cherish predictability but plan around worst-case scenarios -- generally say they have seen improvements in security flows at Logan, but wish it was more dependable.
Carl M. Rubin, a co-owner of Needham technology firm Monument Data Solutions LLC who flies almost weekly to Washington's Dulles International Airport, said, "I have traveled on the same day every week to the same destination, yet every once in a while the lines are very long. I don't know why, because it seems the same number of TSA workers are working."
Added Alan Gold, chief marketing officer for Avotus Corp., a Burlington telecommunications consulting firm that also has a Toronto office: "From my view in Terminal B, no way has it gotten better either in terms of time or in terms of security. I do not ever see enough lanes open to manage the traffic properly, even though sometimes there are screeners milling."
But others give the TSA -- and just as important, their fellow travelers -- good marks for making security lines faster. "The procedure does feel a little more efficient," said Brian LeBlanc, a technology consultant from Gardner who flies on Continental Airlines to Houston every week.
Diana Jennings, a NASA consultant from Falmouth, said she thinks a big reason lines have improved in the last three years is that more travelers know to take off their shoes and belts and collect metal items from their pockets well before they get to the X-ray screeners. "Check-in is more efficient, in part because we customers know the drill," Jennings said.
Marlin W. Collingwood, a managing director with the public relations firm Bell Pottinger USA, said that "what really gets me is that frequent travelers who know what to do to get through the line in quick order can get stuck behind the once-a-year traveling family of five."
To shrink security waits further for travelers, the TSA has tested so-called registered traveler programs that offer a special, reserved check-in for frequent fliers willing to share extensive personal information with the TSA and submit to eye and fingerprint scans.
At Logan, American Airlines offered a pilot registered traveler program in terminal B, but it ended Sept. 30 and the TSA currently has no plans to restore the program before June.
George N. Naccara, the TSA's federal security director at Logan, said the agency has taken many steps to cut waits at Logan's 12 checkpoints. TSA studies airline data on flight departures every hour -- down to what kind of aircraft will be used and how many seats it has -- to decide how to allocate the 130 checkpoint screeners deployed at peak times.
For international flights, screeners fluent in various languages are sent to help non-English-speaking travelers. Since 2002 about one-third of the 800 TSA Logan staff have been cross-trained to be able to switch between screening baggage and people as needed.
"So much of this really relies on communications," said Naccara, referring to airlines, officials of the Massachusetts Port Authority, which runs Logan, and the State Police. "None of us can solve the problem alone."
When security waits exceed 30 minutes, there has usually been an unusual confluence of events.
For example, when it took more than 30 minutes to get through security at Terminal D during three hours on the morning of Monday, Oct. 17, TSA spokeswoman Ann Davis said it had to do with having more passengers than usual, including several flagged for extra screening, and having several screeners pulled off checkpoint duty for explosives-detection training.
To get a sense of average and maximum security waits at any airport over the past month at a specific checkpoint and time, travelers can go to TSA Web site, www.tsa.gov/public.
But while it wants to minimize security waits, at the end of the day, Naccara said, the TSA's top priority remains keeping terrorists off airplanes. "It's shortsighted to use wait time as a gauge" of the TSA's performance, Naccara said. "We're here for security. We like to have a very positive deterrent factor with what we do."