Should we be allowed to carry knives on planes?

It doesn't sound like a great idea, does it? But there's a case for relaxing knife policy on the planes, albeit a "callous and ugly one", and Slate's William Saletan has stepped up to make it.

First off, if you want to make a sharp weapon on a plane, there's an app for that it's not too difficult. You can buy a wine bottle and break it;  bring in some DIY and make a blade from a key, ruler, soda can and some duct tape. Got a pen? Sharpen it - you're a dangerous force. Banning knives does not negate the threat of stabbing.

America's Transport Security Administration (TSA) has called for its screeners to stop confiscating knives less than 6cm in length - saying they're ubiquitous, not a huge threat, and distract from greater security fears.

The flight attendant's union isn't happy with the idea (and they have a point). Pilots are protected by barricaded flight deck doors; attendants only have snappy uniforms and the heroism of fellow passengers to protect them.

This debate is just one example of a shift towards "risk-based security", whereby resources are allocated on the basis of risk, rather than attempting blanket coverage of all possible security breaches.

What do you think? Should we be allowed to carry on Swiss Army Knives?