The maximum carry-on baggage allowance varies by airline, but the international standard for most major carriers is a bag with dimensions of 22 x 14 x 9 inches (56 x 36 x 23 cm), including handles and wheels. In 2026, many "Legacy" carriers (like Delta or Lufthansa) allow for a weight limit of around 15 to 22 lbs (7 to 10 kg), though U.S. domestic airlines often do not enforce a specific weight limit as long as you can lift the bag into the overhead bin unaided. In addition to the main carry-on, you are typically allowed one "Personal Item" (like a purse, laptop bag, or small backpack) that must fit under the seat in front of you. Be extremely cautious with Ultra-Low-Cost Carriers (ULCCs) like Spirit, Ryanair, or Frontier; their "Base" fares often include only the personal item, and any bag meant for the overhead bin requires a substantial extra fee. Always check the specific "Contract of Carriage" for your airline, as some smaller regional jets have much smaller overhead bins that will force you to "gate-check" even a standard-sized carry-on bag before you board.