Carry-on weight limits are notoriously inconsistent across airlines and depend heavily on whether you are flying with a "legacy" carrier or a "low-cost" carrier. Major US airlines like Delta, United, and American generally do not have a specific weight limit for carry-on bags, as long as you can lift the bag into the overhead bin yourself. However, most international and budget airlines are much stricter. British Airways is famously generous, allowing up to 23kg (51 lbs) per bag, while European budget lines like Ryanair or easyJet often limit you to 10kg (22 lbs). In Asia and Australia, carriers like Qantas or AirAsia are even more restrictive, often enforcing a total weight limit of just 7kg (15 lbs) for all cabin items combined (including your personal item). It is crucial to check the specific policy for every leg of your journey; if your bag is even 1kg over the limit on a budget flight, you may be forced to pay a gate-check fee that can cost more than the flight ticket itself.