Checked baggage refers to any luggage that is transported in the aircraft's cargo hold and is not accessible to the passenger during the flight. In 2026, the industry is moving toward a stricter "standard" where any bag exceeding the carry-on limit of 22 x 14 x 9 inches (including wheels and handles) must be checked. This includes large suitcases, duffel bags, and specialized items like strollers, car seats, golf clubs, and skis. Most airlines allow you to check up to 5 or 10 bags for a fee, with a standard weight limit of 50 lbs (23 kg) per bag; exceeding this results in high-value "overweight" surcharges. For 2026 travelers, it is a "pro-move" to note that "Gate-Checked" bags (those taken at the boarding gate because overhead bins are full) are technically checked baggage, but usually don't incur a fee if they meet carry-on size. Always use a TSA-approved lock on checked items, as these are the only bags federal agents are authorized to open and inspect out of your sight.