When officials put Ajaj through secondary inspection, they discovered bomb making instructions and other materials in his luggage, and arrested him.

Firearms (legal to import, but specific paperwork must be filled out and a secondary inspection is usually required)

Now every smart frequent flier knows generally how to avoid being tagged for a secondary inspection.

The ability to predict the likelihood of a secondary inspection is one of a potential terrorist's main strategic assets.

Officials can send a vehicle to "secondary" inspection, where other border officials conduct a thorough search.

Regulations say you are not required to remove shoes, but if they set off the metal detector, you'll get a secondary inspection.

"I have been pulled into secondary inspection about a dozen times since I became a private citizen," he said.

They have said many foreigners, especially asylum seekers, have been mistreated during secondary inspections.

They would have faced a whole range of penalties, starting with the practice of secondary inspections of arriving passengers.

The carpet cleaner was flagged during a secondary inspection.