We have always brought a wax block of extra aged cheddar, with no problems.  We do bring a small cooler, and it goes in there if there is room.  Sometimes no room.  Either way, it stays fine, tastes great on crackers, and melts no problem if sliced thin.  Only on hot trips near the end does it get a little greasy, at worst, and still tastes great.

Only way to fly IMO.  However, born in WI and real cheese is the only allowable food in our house, kind of brainwashed that way!  No "pasturized processed cheese spreads or slices"  make it into the grocery cart!!!  But no one can question the flavor difference.  That is of course if you like real cheddar flavor!  

Give me a 4 year old sharp cheddar on crackers with a little wine, heaven!