I once saw a sign at the El Paso airport that stated. No blades longer than 3.75 inches allowed as carry on. But, I have been to Mainland China four times carrying a 5 inch Cold Steel Voyager in checked in luggage, and a Benchmade A.F.C.K. in my pocket. The A.F.C.K. has also been to Africa and France with no problems. The only problem I have run into was in Newark, N.J., on a lay over to Canada. The girl at the metal detector looked at it closely. I stated, " 4 inches is the maximum limit for carry on isn't it." After talking to the male guard they let it pass. I guess it depends on the guard. Just don't take one you can't leave at the guard gate. <br><br>