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Join Date: Feb 2010
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Unlike say easyJet, I don't think flight crew would announce passengers' birthdays, let alone b'not mitzvah. I think the cake idea is the best one, just get a small one into an exquisite box, and sneek it to the senior crew member to serve it an appropriate point. You may need to give some gentle guidance about this, I suspect b'not mitzvah aren't necessarily well understood by all crew. I can't see the problem with bringing a cake with you, it's not restricted by security controls unless it's very gooey.
And best wishes to your daughter for the future ahead of her.