You may have noticed a three letter acronym on your plane ticket, or next to your departure and arrival city when you’re booking your flight online. Maybe you even refer to your airport as a three-letter code—JFK in New York, or LAX in Los Angeles.After all, every official airport in the world—from the largest, Hartsfield–Jackson Atlanta International Airport (ATL), to the smallest, Juancho E. Yrausquin Airport on the Caribbean island of Saba (SAB)—is assigned a three-letter code. But what does that code mean, and how are they assigned?
Two official entities assign distinct codes to every airport. The International Civil Aviation Organization (ICAO), an arm of the United Nations that ensures aviation regulations jive across different countries and continents, assigns codes generally used by air traffic control and by airlines in crafting their flight plans. Those codes are actually four letters long: The first letter describes the country, and the remaining three letters mark the specific airport. For instance, Florida's Fort Lauderdale-Hollywood International Airport would be KFLL; the “K” is for U.S. and “FLL” is the specific airport code.
There’s LOL (Derby Field airport in Nevada, serving Lovelock City); OMG (Omega Airport in Namibia); and EEK, (a small town in Alaska).
The International Air Transport Association (IATA), an airline trade association, assigns the airport codes you're most familiar with—the three-letters you’ll see when you're booking your flight or on your ticket. Fort Lauderdale-Hollywood International Airport, for example, appears as “FLL," and Amsterdam Schiphol Airport is “AMS.” Sometimes the code is the same as the last three letters that the ICAO assigns, but not always.
Airport coding first began in the 1930s, and airlines typically chose their own two-letter codes. By the late 1940s, there were too many airports, and the system shifted to the three-letter code we know today. Los Angeles International Airport, for instance, was originally just “LA,” but became LAX in 1947. The IATA stepped in during the 1960s when the airlines decided they needed a standardized process to avoid confusion.
“IATA codes are an integral part of the travel industry, and essential for the identification of an airline, its destinations, and its traffic documents. They are also fundamental to the smooth running of hundreds of electronic applications which have been built around these coding systems for passenger and cargo traffic purposes,” Perry Flint, IATA’s head of corporate communications for the Americas, tells Condé Nast Traveler.
The three-letter code is determined by first ensuring that it’s unique and not in use by any other entity. The code might be assigned based on the name of the airport, the name of the city, or some other meaningful and relevant identifier if those letters are already taken. No two airports share the same IATA code, though officials say it's possible we'll have to rethink the process if more crop up than there are three-letter combinations to assign (this isn't likely to happen anytime soon).
Some airport codes are easy to unpack: Miami International Airport is MIA; Athens International Airport is ATH. Other airport codes are harder to decipher. Louis Armstrong New Orleans International Airport’s code, for instance, is MSY, named after aviator John Moisant, the first to fly across the English Channel with a passenger, and who lived in Louisiana until his death in 1910. Chicago O’Hare’s airport code is ORD, named after the space’s previous incarnation as Orchard Field.
