I use a big cheap duffel bag to check my backpack. I'm not willing to risk damage to my backpack-- if the straps get ripped off or the waistbelt gets damaged, it's trashed and hard to carry. The duffel is not that heavy and doubles as a pack fly if it's raining. Friends of mine who are more weight conscious pack a couple of big trashbags and wrap their packs in a trashbag to prevent airline damage-- weighs almost nothing, costs almost nothing.