Those who exhibit questionable behavior would be questioned -- politely. Less than satisfactory answers would lead to further questioning in a more private setting, enhanced screening, the assignment of an air marshal to a specific plane, or the passenger being delayed for further scrutiny. Also: Who should the TSA hire and train for these positions? I would suggest they reach out to retired police detectives, FBI agents and journalists -- people who have already spent decades asking questions and judging responses.
Set Up a Travelers' Registry: Make it voluntary so the American Civil Liberties Union has no cause for apoplexy. I doubt I'm alone in my willingness to let airport security know as much about me when I travel as American Express does when I buy a pair of shoes. Being a registered traveler will not exclude anyone from security checks. But it could make traveling a bit easier while helping security officials establish priorities.
Fix the Visa System: Currently, visas are stamped by the youngest, least experienced Foreign Service Officers. They generally hate it but they have to do it for a few years. It's now clear we need professional consular officers who will ask hard questions and make tough decisions - like not giving a multiple entry and exit visa to a 23-year-old Nigerian student with a checkered history. (You think Nigerians authorities easily give such visas to Americans? When I was West Africa bureau chief for The New York Times I couldn't get one.)
Homeland Security, rather than the Foreign Service, should assume responsibility for visas. And, again, I'd suggest hiring people trained to be suspicious, like retired cops and reporters. Then train them again, specifically for these jobs.
Use Advanced Technology: Former Homeland Security Secretary Michael Chertoff recently pointed out that most airport security checkpoints use metal detectors which can't detect explosives such those used by Abdulmutallab and "shoe bomber" Richard Reid in 2001.
Chertoff suggests instead using "whole-body imagers" which, he believes, would "detect non-metal weapons concealed by terrorists on their bodies -- even in their underwear, where Abdulmutallab allegedly hid his bomb."
Various groups, citing privacy concerns, oppose the use of imagers, and in June the House passed a bill that aims to limit their use to passengers selected for additional scrutiny. Chertoff may be correct to argue that it's safer to have every passenger pass through a high-tech imager. But coupled with my first proposal above, at least all those we might call "passengers of interest" would be "imaged" before boarding a plane.
Fix What Else Is Broken; Stay on Offense: Airport security is not the only feature of our national security architecture that was poorly designed. Intelligence is also among the areas where reform has not succeeded and needs to start again.
Big picture: The goal must be nothing less than the defeat of militant jihadists. These ruthless and determined enemies must be sought out where they hide, train and plot; they must be eliminated when possible; kept nervous and uncomfortable when not. Very few should ever manage to arrive at an airport trained and equipped to commit mass murder. But that's another column for another day.