The best carry-on luggage

Qantas allows an overhead cabin bag up to 56 x 36 x 23 cm. In international economy the limit is 7 kg, and in domestic economy it is 14 kg in total with no single item over 10 kg. Other airlines, especially budget carriers like Jetstar, set their own rules, so check your booking before you fly.

Yes. Airlines measure the whole bag, including wheels, handles and any outside pockets. Many US-market 21 or 22 inch bags measure 58 to 60 cm with wheels, which is over the 56 cm limit used by many airlines outside North America.

Hardshells made from polycarbonate protect fragile items well and shrug off rain, but they scuff and usually do not expand much. Softsides made from ballistic or coated nylon usually have handy outside pockets, squeeze into a full overhead bin more easily and often expand. Either can be very durable if you buy a good brand with a strong warranty.

Expanding adds a few centimetres of depth, which can push a bag over the cabin size limit. Keep it zipped closed when you fly with it as hand luggage, and use the expansion when you plan to check the bag on the way home.