First, print out a copy of the TSA rules for carrying a firearm as checked luggage. Then print out the specific rules for each airline you will be flying on. You need to be in compliance with both sets of rules. I recently flew Colorado Springs to SF, on United. United rules require a hard sided case specifically built to carry firearms. They also require either combo or key locks, with the key in your possession. They do NOT have to be TSA locks. I went down to the local hardware store and bought a set of 4 Master padlocks, keyed alike. My check in was the same as Timh: Explain you are checking in a firearm in compliance with all the rules, sign the acknowledgement form, get escorted to TSA where they watch you unlock and open case. TSA then inspects contents, puts a card inside, and asks you to relock everything. They put a sticker on the outside, saying it had been inspected, and away it went. Picked it up at destination with no trouble.