I've had mine in my carry-on for years. The main blade is about 4 1/2" long. Also a saw of the same length...
Never been questioned about it even once.
At ZRH they sell tons of Swiss Army knives airside. The sales people say all the knives they are selling are okay on all their outbound flights...and some aren't so small!!
Dorian
------------------
flyers'places - restaurant, bar & hotel recommendations:
http://www.flyersplaces.com
Dorian's Star Alliance RTW Price Chart:
http://www.informationlab.com/rtw.htm
Blondebomber's Star Alliance Comparison Chart:
http://members.home.net/deercroft/starall00.html