Both the TSA and the FAA, the agencies responsible for travel safety and regulations, have well established laws and rules for the transportation of arms and ammunition. Even if the weapon or firearm that is being transported is for airsoft or paintball, these guns are treated with the same security as real guns and failure to follow the regulations which can result in serious penalties.
It is important to remain up-to-date with all FAA and TSA laws as increases or decrements in threat levels can affect whether certain particular rules are being suspended or adjusted. Also be sure to check the rules of the airline and, if you are traveling outside of the US, the local government. Some airlines have more lax rules about traveling with guns, while some prohibit it entirely. Similarly, many countries have bans on guns, even airsoft guns. Countries including Canada, Thailand and Singapore prohibit airsoft guns so be sure to inform yourself of your destinations laws regarding airsoft.
If possible, it is preferred to stow and lock your firearm in a box so that it remains secure through the flight, does not jostle, and is easily identified. Whether or not your firearm has its own separate case, it must be enclosed in a hard-sided item.
No guns will be allowed that are stored in soft suitcases, duffel bags or other soft-sided baggage. A hard-sided, molded case that snugly secures the gun is best. It is also necessary for any luggage that is storing the gun to have either a key or lock on it.
Be sure to provide either the key or the combination for the lock to the security officer in the case that he or she needs to open the container. You should remain present during the screening to retrieve your key after the container is cleared. If you are not present and the security officer must open the container, the airline will make a reasonable attempt to contact you. If TSA agents can not contact you, the container will not be placed on the plane.
Additionally, federal regulations prohibit unlocked gun cases or those with broken locks on aircraft, so be sure that your luggage and / or lock are in good condition prior to departure for the airport.
Check with the airline to find out the amount of ammunition that is allowed to be packed for flight.
No ammo, pellets or airsoft bbs may be loaded in the gun. All ammunition that is packed in suitcases must be securely store in a cardboard, metal or wood box. Other boxes specifically designed to carry ammunition are also accepted by the TSA. Be sure that the box is an adequate size for the amount of ammunition; that is, neither too large that the ammunition is left loose and jostling inside, nor so small that the box has difficulty remaining closed.
If the ammunition is to be stored within the same case as the gun, it must still be individually packed within a box. If you are traveling internationally, please check with the authorities at your destination about their requirements.