Those last two individuals weren't caught for suspicious behavior. They were caught after actually lighting up in the plane enough to create some smoke.

On the day when the failed "shoe bomber" named above boarded a plane and attempted his dirty deed, as on the day when the failed "underwear bomber" named above boarded a plane and attempted his dirty deed, persons trained to detect "suspicious behavior" questioned the failed "bomber" and cleared the failed "bomber" to travel.

.... and these were the "mature", "trained" "specialists", unlike the flight crews or -- better yet -- 6-months old babies, who cleared them for travel.