It's not necessary to vacuum seal meat, but it helps to make sure that it keeps frozen, AND if it were to become unfrozen, it keeps in all the juices. As far as carry on, we only take enough for the two of us, so we always do carry on. That really helps, if you were to become 'estranged' from your checked bags. I don't have a Polar Bear cooler myself, but if I were checking meat, I might well invest in one. As others have said, freeze EVERYTHING including the cooler for at least a couple of days before you leave, which will help things stay frozen. If everything is frozen solid before, no need for anything except the meat, to keep it frozen, for a trip JFK to STT.