Knives in checked luggage should not pose any problem. I have flown for years and never ever had anykind of problem. In their rules here passengers are required to make sure that sharp objects such as knives be properly wraped and sheathed to prevent injury to baggage handlers as there have been cases of unsheathed knife blades protruding from suitcases.
On internation flights make sure you know the rules and laws of the country you are visiting. Don't carry lockback folders to England, they will confiscate them and give you a hard time (maybe even time). On domestic flights I carry whatever knives I want in the checked luggage. On international flights where customs is involved I take knives that are legal for the country I plan to visit, and keep the fixed blade length at 5 inches or less to avoid being noticed. Big bad blades are better left at home.
