Checked baggage encompasses items accepted during check-in for placement in the aircraft's cargo compartment, subject to specific regulations. Passengers, based on their ticket class, receive a complimentary baggage allowance, with the option to purchase additional rights for extra baggage. Conversely, cabin baggage regulations vary by airline cabin class, specifying the number and weight of bags passengers can bring onto the plane. Baggage allowance refers to the entitlement of passengers to bring a specified number and weight of checked and cabin baggage, included in their purchased tickets and defined by airlines in terms of both quantity and weight. Checked baggage is transported in the plane's cargo compartment under the airline's responsibility, subject to airline-specific rules, which all passengers are expected to adhere to.