Amid the departure gates, terminals, Hudson News stores, and airline lounges at airports lies a hidden language, recognizable to frequent travelers and aviation enthusiasts alike: the three-letter airport code.
From the familiar JFK and DFW to the more obscure ORY and AKL, these codes are more than random letters—they hold the key to identifying airports worldwide. But what do they mean and how exactly do airports acquire these unique identifiers?
In the early days of aviation, pilots in the United States referred to airports using the same two-letter city identification system as the National Weather Service. However, as the number of airports grew, it was necessary to expand to a three-letter code system that would allow for more options. (The three-letter combination gives 17,576 possible codes, whereas two letters only allow for 676.) To make it easier, in some cases, an X was added to existing airports, which is why LA became LAX.
It wasn’t until the 1960s that the Montreal-based International Air Transport Association (IATA), a trade association for the global airline industry, took on the task of assigning these codes, aiming to create a simple and uniform method for identifying airports across different countries and languages. When a new airport is planned or an existing one undergoes significant changes, the relevant authorities submit a request to IATA for an official three-letter code. This request typically includes details such as the airport’s location, name, historical background on the area, and some suggestions of codes that officials at the airport would like to have considered.
The first choice of IATA is to create an airport code using the first three letters of the city’s name, such as LAS for Las Vegas or BOS for Boston. Alternatively, especially if there is more than one airport in a city, it chooses an abbreviation for the airport, like JFK for John F. Kennedy International Airport in New York. The second choice is to use a combination of letters from the name, preferably starting with the same first letter as the city, such as AHN for the airport in Athens, Georgia.
Occasionally, this leads to some fairly humorous codes like LOL for Derby Field Airport near Lovelock, Nevada, and SUX for Sioux Gateway Airport in Sioux City, Iowa. (Another fun code is OMG for Namibia’s Omega Airport.)
No two airports can share the same three-digit code. So if an identifier can’t be created for a new airport using those methods, occasionally the code will be a nod to the history of the area. For example, present-day Orlando International sits on the land that was once McCoy Air Force Base, hence why its airport code is MCO. Similarly, Hawai‘i’s Kahului Airport in Maui has an airport code of OGG—it’s a tribute to a former Hawaiian Airlines pilot, Captain Jimmy Hogg, who operated the company’s first trans-Pacific flight.
IATA also gives codes to ferry, bus, train, and helicopter terminals that share ticketing and baggage transfers with airlines—it helps keep baggage handling and bookings running smoothly. Currently, about 11,300 codes are assigned; according to the IATA, roughly 40 to 50 new codes are doled out each year. Once a code is assigned, it is almost never changed. For example, even though the airport in Oakland, California, recently voted to rename itself San Francisco Bay Oakland International Airport, it will keep its OAK three-letter code. However, according to IATA, if there’s a concern over air safety, they may choose something else. That’s what happened when Washington Dulles International Airport was changed from DIA to IAD to avoid confusion with the nearby Ronald Reagan Washington National Airport (DCA).
To make matters slightly confusing, there’s also a competing four-letter code used internationally—but you might never come in contact with it. In addition to IATA, the International Civil Aviation Organization also issues airports a four-letter code. ICAO simplifies the code even more by making sure the first letter always corresponds to what region the airport is in, so all U.S. airports start with a K and all Chinese airports start with a Z. However, you’re unlikely to come across these longer codes—they’re primarily used by air traffic controllers and air navigation service providers, whereas the IATA code is for the general public’s use.
