Print a copy of the specific airlines' rules.Then print this page and keep it also:
http://www.tsa.gov/travelers/airtrav...rial_1666.shtm. Follow them TO THE LETTER,and keep copies with you,not all airline employees are aware of their own policies regarding firearms.
Make sure you have a good quality gun case,preferably one that has lock holes on the sides,like a Doskicil.If the TSA officers determine that your case is too flimsy,they will not let you use it,and IF the airline has any available,it will be expensive...There are guidelines for this on the TSA website...
TSA approved locks are available at WalMart for under $10,they should have a TSA symbol and number printed on the lock.If you use a TSA marked lock,there's no need to hand over your keys,they will have a key that works,and they will appreciate the fact you paid attention to the rules.
When he arrives at the check-in counter,say "I'd like to declare a firearm",the airline will have a "Declaration of Unloaded Firearm" form.Fill it out,or let them fill it out,depending on their policy,and then you will give your bag to a TSA officer who will inspect it for compliance,(again,follow TSA guidelines TO THE LETTER),they will lock it back up,and you're on your way.Your luggage will come down the carousel with all the others at the baggage claim area when you arrive...
TSA "should" take care of it for you,but DO NOT allow the airline employees to put an external tag on your luggage ID'ing it as having a fiream inside,this is illegal,the "firearm" tag goes inside.