A friend flew to Istanbul in 2017 and landed at an airport with the code IST. I flew to Istanbul in 2022 and also landed at IST. Same three letters, completely different buildings, twenty miles apart. So when someone asks whether airport codes can change, the honest answer is: almost never, and yet the codes have a habit of walking out the door and following the passengers.
The Istanbul story is the cleanest example of how this works. In 2018 the brand-new Istanbul Airport opened and the IST code packed up and moved there. Ataturk Airport, the original holder, got ISL in exchange. Same city, same code, different runway. It feels like a contradiction until you understand whose code it really is.
So can airport codes change, or not?
Both, depending on what you mean. The International Air Transport Association, which assigns the three-letter codes, is blunt about it: codes cannot be changed unless there is a strong justification, and a request must go through the IATA customer portal with a detailed explanation. Marketing and branding do not count. IATA has said plainly that a renamed airport is not grounds for a change, because hundreds of electronic systems are built around these codes: reservations, baggage routing, cargo manifests, flight plans. Swapping letters would be like renumbering every highway in America at once.
And yet codes do move. The pattern is consistent: the code belongs to the city gateway, not to the concrete. When Bangkok opened Suvarnabhumi Airport as its larger international facility, the BKK code moved there from Don Mueang. The old airport kept operating with a different identifier. IATA calls codes "fluid" in exactly this sense. They are not carved in stone; they are pinned to the airport that serves the city's main traffic.
| Code | Originally | Now | What happened |
|---|---|---|---|
| IST | Istanbul Ataturk | New Istanbul Airport | Code followed the new main gateway (2018) |
| BKK | Don Mueang | Suvarnabhumi | Code followed the larger airport |
| ORD | Orchard Field | O'Hare | Code kept after rename and growth |
| LAX | LA (2 letters) | Los Angeles | X filler added in the 1940s; never changed |
What survives every rename
Most of the weird codes you know exist precisely because changing them is impractical. ORD comes from Orchard Field, the name of the place before it became O'Hare. Nobody would name an airport ORD today, but every booking system on the planet expects those three letters for Chicago. YYZ comes from a legacy radio beacon code in Toronto. Same story. The codes are published twice a year in the IATA Airline Coding Directory out of Montreal, and the list is a layer cake of history: the most sensible letters were taken first, and everything since is negotiated around what is left.
This is also why you should never "convert" between code systems yourself. An IATA code and an ICAO code for the same airport are assigned independently. The K-prefix rule gets you close in the United States, but the general principle holds: if you need the code, look it up rather than deriving it.
The practical lesson for travelers
Here is where this stops being trivia and starts being useful. When you book a flight, the code tells you the city gateway, not necessarily the terminal you will walk through. Cities with two airports make this obvious, but even single-code cities can surprise you years later when a new airport inherits the code. Before you book a hotel, a ride, or a connecting flight, check the airport's actual name and address, not just the three letters. The letters are stable. The buildings are not.
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It is a weirdly satisfying system once you accept it: the codes are designed to be permanent for the computers and quietly flexible for the cities. IST will probably outlive every terminal it ever marks.
Frequently asked questions
Can an airport's IATA code be changed?
Yes, but rarely. IATA requires a strong justification, submitted through its customer portal. A renamed airport is not grounds for a change; changes typically happen when a new airport replaces the old one as the city's main gateway.
Why did Istanbul's IST code move to the new airport?
When Istanbul Airport opened in 2018, IST transferred to it from Ataturk Airport, which received ISL. The code follows the city's primary international gateway.
Who decides whether a code changes?
The International Air Transport Association. Codes are published twice yearly in the IATA Airline Coding Directory from its Montreal headquarters.
Does an airport keep its code after a rename?
Yes. Codes stay even after full renames because reservation systems, baggage handling, and cargo operations worldwide are built around them.
What happened to Bangkok's BKK code?
BKK originally belonged to Don Mueang Airport and moved to Suvarnabhumi Airport when it opened as Bangkok's larger international gateway.
Sources: IATA code-change policy; Simple Flying, "Explained: The Most Obscure Airport Codes In The US"; AeroXplorer, "Understanding IATA Codes." Figures verified October 2026.