** REALLY IMPORTANT **
Check the status of CA SB199 BEFORE you fly. If it passes as-is and your gun is not a bright color then you could be arrested for possessing it.
This facebook page will have up to date information on the proposed bill:
https://www.facebook.com/nosb199
For entry and travel within the United States:
1) No orange tip is required unless you are going to sell it (Orange tip regulation is a commerce regulation.)
2) You should have it in a hard sided locking case - this is required for real guns but not for airsoft, however someone looking to steal your gun might not know the difference. If it is a pistol you could put the hard case inside of your suitcase and lock it to the handle rail on the inside.
3) Do not bring any gas or CO2 at all - MAGS MUST BE EMPTY OF GAS!
4) Declare it as an airsoft gun to the airline when you check in
5) Give yourself an extra 1/2 hour for airport check-in as everybody at every airport has a different opinion of what the rules are.
6) Within the US you don't need a unique serial number but seeing the above posts it seems like the best idea.
Here is the official TSA blog (
http://blog.tsa.gov/) on airsoft when flying:
http://blog.tsa.gov/2013/07/tsa-trav...ling-with.html
I normally check mine in a Peilcan case (I have a Pelican 1700 that fits two M4's and one pistol) and lock it with two master locks (not TSA locks.) I declare an airsoft gun at the counter and 9 times out of 10 the airline agent makes me fill out a firearms declaration card (for a real firearm.) They mostly don't know the difference and really are not trained to.