An IATA airport code, also known as an IATA location identifier, IATA station code, or simply a location identifier, is a three-letter geocode designating many airports and metropolitan areas around the world, defined by the International Air Transport Association (IATA). The characters prominently displayed on baggage tags attached at airport check-in desks are an example of a way these codes are used.

Bag tags, also known as baggage tags, baggage checks or luggage tickets, have traditionally been used by bus, train, and airline carriers to route checked luggage to its final destination. The passenger stub is typically handed to the passenger or attached to the ticket envelope: to aid the passenger in identifying their bag among similar bags at the destination baggage carousel; as proof—still requested at a few airports—that the passenger is not removing someone else's bag from the baggage reclaim hall; and as a means for the passenger and carrier to identify and trace a specific bag that has gone astray and was not delivered at the destination. The carriers' liability is restricted to published tariffs and international agreements.