All You Need to Know About the IATA Codes

International Air Transport Association (IATA) airport codes are location identifiers, much like ICAO codes. However, the purpose of both are different. While air traffic controllers mostly use ICAO codes, IATA codes are mostly used on tickets, baggage tags, and other airport services. It's used extensively by airlines to help passenger and luggage transfers.

In fact, IATA codes aren't just used for airlines. Sometimes they are also used for the railway stations and airport handling entities. Historically, it started out as two-letter system, which was used by National Weather Service for identifying cities in United States. With time, it became difficult to manage things as the air traffic grew. Therefore, the system was changed to a three-letter system.

Structure and how the codes are made

Airports are coded normally based on the first three letters or the combination of letters of the city's name; such as ATL for Atlanta, MEX for Mexico City, and JNB for Johannesburg.

The convention isn't a rule. Custom Conventions are sometimes used in the name taking into account factors like the country, airport name, or even municipality region in which the airport is situated (common when there are multiple airports in the same city). Here are a few other custom conventions for assigning IATA code.

  • In case, a city has two airports like metropolitan cities of New York use, the airports name to designate the IATA code. For London's airport, Heathrow uses LHR; Gatwick uses LGW, London City uses LCY, and so on. And in case, the reverse occurs, such as two cities has the same name than different codes are assigned to differentiate both cities.
  • When a new airport comes up in the city apart from the older one, or there are two airports within the city, the code for the two airports cannot be the same. This is because of the rules, that states that first and second, second and third letters of identifiers cannot be duplicated within 200 nautical miles. Hence, different identifiers are used to separate it from duplicate city.
  • Sometimes codes are based on the old names of airport such as Chicago's O'Hare use ORD that was Orchard Field before.


The exceptions are many and sometimes airports use the historical name of the city - for instance Kolkata airport that was named Calcutta earlies, uses the code CCU.

  • US Navy has reserved N codes while Federal Communication Commission has reserved W, and K for themselves. Hence, cities that begin with these letters adopted different letters for instance , Mumbai use BOM and Chennai use MAA.
  • All Canadian airport use codes that begin with Y such as YVR for Vancouver. However, all codes beginning with Y are not Canadian airports. Similarly, most of the New Zealand airports use Z letter.