Flying with firearms domestically has not changed very much since 911, however, you are advised to check with the Airline you are flying.
Black powder is never allowed on a commercial aircraft.
Traveling with Special Items (This information was taken directly from the TSA website on 3/19/08) **Please check their website for changes or updates)
Go to: www.tsa.gov
Firearms & Ammunition
There are certain limited exceptions for law enforcement officers who may fly armed by meeting the requirements of Title 49 CFR § 1544.219. Law enforcement officers should read our policies on traveling with guns.
The key regulatory requirements to transporting firearms, firearm parts or ammunition in checked baggage are:
• You must declare all firearms to the airline during the ticket counter check-in process.
• The firearm must be unloaded.
• The firearm must be in a hard-sided container.
• The container must be locked.
• We recommend that you provide the key or combination to the security officer if he or she needs to open the container. You should remain present during screening to take the key back after the container is cleared. If you are not present and the security officer must open the container, we or the airline will make a reasonable attempt to contact you. If we can’t contact you, the container will not be placed on the plane. Federal regulations prohibit unlocked gun cases (or cases with broken locks) on aircraft.
• You must securely pack any ammunition in fiber (such as cardboard), wood or metal boxes or other packaging that is specifically designed to carry small amounts of ammunition.
• You can’t use firearm magazines/clips for packing ammunition unless they completely and securely enclose the ammunition (e.g., by securely covering the exposed portions of the magazine or by securely placing the magazine in a pouch, holder, holster or lanyard).
• You may carry the ammunition in the same hard-sided case as the firearm, as long as you pack it as described above.
• You can’t bring black powder or percussion caps used with black-powder type firearms in either your carry-on or checked baggage.
Airlines may have their own additional requirements on the carriage of firearms and the amount of ammunition that you may have in your checked baggage. Therefore, travelers should also contact the airline regarding its firearm and ammunition carriage policies.
Also, please note that many other countries have different laws that address transportation and possession of firearms. If you are traveling internationally, please check with the authorities at your destination about their requirements.