Checked Baggage only. For a milsim marker I'd defintely make someone aware of what is in the bag.
Print out a copy of the TSA regulations and stick one in your bag, keep one with you: https://apps.tsa.dhs.gov/mytsa/cib_r...arch=paintball
You'll need to remove the regulator on any air tank, they need to be able to look into the cylinder. You can put the reg back on when you get to the event, finger tight is fine, the pressure holds the reg in.
If you don't have a hard bag for your gear, consider either a hard case for your mask like Exalt's or you can take that as a carryon.