You should be able to carry them in your checked baggage, but you won't be able to carry them on. The policy is to keep any potential weapons off the plane. That basically means that anything that even looks dangerous can be barred. For instance, I recently had to mail a keychain to myself because it had a replica bullet and shell on it. There's no way it was dangerous, but they don't want to take any chances. Dismantle them as much as possible and place them in your checked luggage. You should go ahead and check with the airport ahead of time, but you shouldn't have any trouble. I've taken a fairly realistic airsoft gun in my checked luggage with no problem.

NO

If you bring it onboard the passengers or crew will be entirely in their rights to attack, subdue, and kill you.

Do not attempt to carry it on. Pack it on top of your checked luggage not in among other things. It will show up on the x-ray scan and your luggage is sure to be opened. Do not lock your suitcase because they will break it open if you do.
Declare it when you check in. Let the ticket agent know what you've got a toy gun in your luggage so there is no confusion and it will let them know that you are not concealing anything. You still may be in store for a hassle. Airline security workers are far from Rhodes scholars.
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