All One Planet travel and hybrid packs have zip sliders that can be locked for extra security.

Many people use small padlocks, but cable ties are another excellent option. They still act as a deterrent to petty thieves, but if customs need to look inside your bag, they simply cut the cable ties instead of your expensive padlock. Carry a few spares for each time you get on a plane – simple.

This presents another problem: what do you use to cut the cable ties now that sharp objects are not allowed in your daypack? Stash a pair of nail clippers behind the lumbar pad of your main pack’s harness and that problem is solved.

If you are travelling with a top-loading pack, you can still use cable ties to secure the buckles. As with lockable zip sliders, it won't stop the determined criminal, but it will deter the petty thief.