Hardshell bags can crack from too much pressure. In this case, you would be forced to replace it with another one, and some airline companies don’t offer compensation for these accidents. In order to avoid such problems, make sure you don’t under pack by leaving more space inside. This way, when pressure is added, the cracking is easier. Overpacking can result in the same problem. This style of luggage is visually looking like they hold more stuff inside. It is comprised out of two parts and it closes with a clamshell method which is connecting the two sides in the middle. You could pack stuff on each side which is more convenient if you are an organized type. However, if you manage to pack more stuff inside, you will probably overpack the luggage which would make the zipper prone to cracking.