I have flown from the UK to Europe and the US many times with armour. As Paul suggests a good hard shell case is best and ask the airline if they have a facillity to walk on fragile items, some do and this helps avoid cases being tossed etc. Fragile stickers also help.
I also carry pics of the armour and blaster and some of me in the armour to show staff and any customs who are interested, to be honest this generally gets them on side too because as we know everyone loves Star Wars!
I also, like Paul carry my helmet on as it is easier.
I hope that helps.
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