We flew JetBlue to St. Lucia with 2 vests and 5 cartridges. Bring a copy of the TSA paperwork. We did it all carry on. They did question it but I showed them the paper work and we were fine.
I believe it says 2 in the vest and 2 spares and 1 vest per person.
I'm not sure why you think its obvious you can't bring it on the plane - you do realize there's one under every seat, right? <img src="http://www.traveltalkonline.com/forums/images/graemlins/Wink.gif" alt="" />
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