I have several large moving boxes from Lowes. Cut some foam sheets to insulate them and fill them with 46# of frozen solid meat. They’ve been back and forth to my parents house a hundred times filled with beef, deer, fish, empty, clothes, toys, you name it. They meet the US airlines maximum dimensions for standard luggage. They fly free on Southwest. If the boxes get too beat up I just get new cardboard and reuse the foam. The meat is always frozen solid when we get it home still. They even misplaced 2 of them full of beef last summer flying through Arizona and they made it in on a later flight the same day as my wife and were fine.