18 Inch Luggage refers to any luggage bag that measures 18 inches in height when measured in the upright position. 18 Inch Luggage bags are considered lightweightcarry-ontravel containers specially designed to hold necessary articles during short trips. Types of 18 Inch Luggage include upright spinners, duffels, and carry-on bags. An 18 Inch Luggage container is an acceptable carry-on size allowed for most airlines.