IATA code in car rental
IATA code is a three-letter code that is used in car rental to indicate a specific airport in the world. For instance, TLL is the IATA code for Tallinn Airport. This three-letter code is defined by IATA (International Air Transport Association).
IATA also provides codes for other locations, such as cities and railway stations. For more information about different IATA codes, please see here.