Air Canada, all dimensions for luggage can be found on every airlines webpages. Box, bag, suitcase, garbage bag it doesn't matter as long as it meets the size and weight requirements. Ive flown 20 different airlines with up to 80 flights a year some years, never been told my piece of luggage wasnt acceptable, been charged for weight, extra bag and oversize but never for style. I once took a muffler with tail pipes wrapped in cardboard, bubble wrap, and duct tape. I had to run around the airport looking for a small piece of cardboard to cover up an exposed piece of metal, and they still let it go through.