On one hand, they carry high-priced items that they want to protect.

FORBES: Why Do People Steal Meat From Grocery Stores?

As well as having to undergo more stringent checks, passengers are also being limited to one piece of carry-on hand luggage.

BBC: Airport security measures

Travellers should also consider printing out boarding passes ahead of time to speed up the check-in process, and should remember the rules about packing liquids and electronics in carry-on and hand luggage.

BBC: Navigating the London 2012 exodus

It therefore seems problematic to me when such lively, well-informed and yet largely unresolved debates get reduced to six key messages, messages that on the one hand carry the aura of urgency, precision and scientific authority - "there is no excuse for inaction" - and yet at the same time remain so imprecise as to dictate or resolve nothing in political terms.

BBC: What message, and whose, from Copenhagen?

On the other hand, searching for the knives on passengers or in their carry-on bags is time consuming, Pistole said.

NPR: TSA Stands By Plan To Allow Small Knives On Planes