What Is an IATA Airport Code and How Are They Assigned?

Every time you check in for a flight, three letters appear on your boarding pass next to your departure and arrival airports. These are IATA codes — a standardized system managed by the International Air Transport Association that assigns a unique three-letter identifier to every commercial airport in the world.

Who assigns IATA codes?

IATA, headquartered in Montreal, assigns codes to airports that request them. An airport must demonstrate it handles regular scheduled commercial traffic to qualify. Once assigned, a code is permanent — it does not change even if the airport is renamed or expands. This permanence is why ORD still represents Chicago O'Hare (originally Orchard Field) and MSY still represents New Orleans (Moisant Stock Yards).

The three-letter system

Three letters give 17,576 possible combinations (26³). IATA has assigned roughly 10,000 of these to active airports, leaving plenty of room but requiring creative choices. Many codes are straightforward: LAX for Los Angeles, LHR for London Heathrow, SYD for Sydney. Others reflect historical names, local languages, or the need to avoid conflicts.

Why do some codes seem random?

In the United States, the FAA had already assigned two-letter codes to major airports before IATA standardized on three letters. IATA simply added a letter — usually X — to create the IATA code. Hence Los Angeles went from LA to LAX. Canada used Y prefixes, which is why YVR is Vancouver and YYZ is Toronto Pearson.

Practical uses of IATA codes

IATA codes appear on boarding passes, baggage tags, airline booking systems (GDS), and flight comparison websites. They are the universal language of commercial aviation for passengers. When you see SEA on your luggage tag, that is Seattle-Tacoma International Airport. When you book a flight to DXB, you are flying to Dubai International.

For a comparison with the parallel ICAO system used by pilots and air traffic control, see our guide on IATA vs ICAO codes.