Airport Codes Explained: IATA vs ICAO

Two codes, two purposes

Every commercial airport in the world has at least two identifiers:

• IATA — three letters, used by airlines, travelers, and luggage tags. Examples: LHR, JFK, SIN.
• ICAO — four letters, used by air traffic control, pilots, and flight planning systems. Examples: EGLL, KJFK, WSSS.

The IATA code is what you see on your boarding pass. The ICAO code is what shows up on a pilot's flight plan and on most flight-tracking radar overlays.

How ICAO codes are structured

ICAO codes encode geography:

• First letter — region (e.g. K for the contiguous USA, E for northern Europe, Y for Australia).
• Second letter — country or sub-region.
• Last two letters — the airport itself.

So EGLL decodes to: E (northern Europe) → G (United Kingdom) → LL (London Heathrow).

In the contiguous US the first letter is always K, and the remaining three letters typically match the IATA code: JFK → KJFK. Hawaii and Alaska are exceptions (PHNL for Honolulu, PANC for Anchorage).

How IATA codes are chosen

IATA codes are looser. Many are obvious abbreviations (LAX, SFO, SYD). Some are historical relics:

• MCO — Orlando International, formerly McCoy Air Force Base.
• ORD — Chicago O'Hare, formerly Orchard Field.
• YYZ — Toronto Pearson; the Y prefix is reserved for Canadian airports.

How to look up an airport code quickly

Type the city or airport name into your flight tracker. In FlightyFlow, the airport detail page shows both codes plus the runway diagram, current weather, and live arrivals/departures.

When you'll need each one

• Booking, baggage tags, conversation: IATA.
• Flight tracking radar URLs, METAR weather requests, pilot tools: ICAO.