Quick Facts
- Topic
- Aviation Identification Systems
- Covers
- ICAO 4-Letter and IATA 3-Letter Codes
- Audience
- Pilots, Dispatchers, Travelers
- Difficulty
- Beginner
Two Systems, One Airport#
ICAO and IATA airport codes are standardized identification systems that assign unique alphanumeric designators to airports — four-letter codes from ICAO for operational aviation use, and three-letter codes from IATA for commercial and passenger-facing purposes.
Every major airport in the world has at least two identifying codes — one from ICAO and one from IATA. These systems serve different audiences and appear in different contexts, but both refer to the same physical locations. This guide is part of Aviatopia's How Airlines and Airports Work series.
What Are ICAO Codes?#
The International Civil Aviation Organization (ICAO) assigns four-letter codes to airports, airfields, and heliports worldwide. These codes are used in:
- Flight plans and ATC communications
- METARs and TAFs (weather reports)
- NOTAMs (Notices to Air Missions)
- Aeronautical charts
Structure#
ICAO codes follow a geographic prefix system:
| Prefix | Region | Example |
|---|---|---|
| K | Contiguous United States | KJFK (New York JFK) |
| C | Canada | CYYZ (Toronto) |
| EG | United Kingdom | EGLL (London Heathrow) |
| LF | France | LFPG (Paris CDG) |
| RJ | Japan (mainland) | RJTT (Tokyo Haneda) |
| WS | Singapore | WSSS (Changi) |
The first letter (or two) of an ICAO code identifies the world region and country. This makes it possible to approximate an airport's location from the code alone.
What Are IATA Codes?#
The International Air Transport Association (IATA) assigns three-letter codes primarily used in:
- Airline ticketing and reservations
- Baggage handling
- Passenger-facing displays (departure boards, boarding passes)
IATA codes are what most travelers recognize: JFK, LAX, LHR, NRT.
Key Differences#
| Feature | ICAO | IATA |
|---|---|---|
| Length | 4 characters | 3 characters |
| Assigned by | ICAO (UN agency) | IATA (trade association) |
| Geographic logic | Yes (prefix system) | No (historical/arbitrary) |
| Primary users | Pilots, ATC, weather | Airlines, passengers |
| Coverage | All aerodromes | Major commercial airports |
| Example | KJFK | JFK |
Why Both Exist#
The two systems evolved independently for different purposes.
ICAO codes serve aviation operations — they need to be systematic, globally unique, and tied to geographic regions for quick identification. A pilot seeing EG in a flight plan immediately knows they're dealing with a UK airport.
IATA codes serve the commercial airline industry — they need to be memorable, short, and easy for passengers to use. Nobody wants to type KLAX when booking a ticket to Los Angeles.
Converting Between Systems#
There's no algorithmic conversion between ICAO and IATA codes. The relationship is maintained through lookup tables. However, some patterns help:
For US airports, the ICAO code is often K + the IATA code. For instance, JFK → KJFK, LAX → KLAX, ORD → KORD.
For Canadian airports, the ICAO code is often CY + two letters from the IATA code. For instance, YYZ → CYYZ, YVR → CYVR.
For other countries, the mapping varies. London Heathrow is LHR (IATA) but EGLL (ICAO) — no simple pattern.
Never assume a simple prefix mapping works globally. Always verify against an authoritative database when filing flight plans or referencing airports in operational contexts.
When to Use Which#
- Filing a flight plan? Use ICAO.
- Reading a METAR or NOTAM? Use ICAO.
- Booking a flight or looking at a departure board? Use IATA.
- Communicating with ATC? Use ICAO.
- Tagging luggage? Use IATA.
Edge Cases#
Not all airports have both codes. Small airfields and private strips may have only an ICAO code (or a national code). Conversely, some IATA codes exist for railway stations and bus terminals used in intermodal ticketing.
Some airports share surprisingly similar codes — EDDF (Frankfurt) vs. EDDB (Berlin Brandenburg) in Germany's ED prefix — so precision matters.
Summary#
Both systems are essential to aviation operations. As a rule of thumb: if you're doing anything operational (flying, weather, ATC), use ICAO codes. If you're on the commercial/passenger side, IATA codes are your everyday standard.
Frequently Asked Questions#
Key Takeaways#
- ICAO assigns four-letter airport codes using a geographic prefix system; IATA assigns three-letter codes without geographic logic.
- ICAO codes appear in flight plans, METARs, TAFs, and NOTAMs; IATA codes appear on boarding passes, baggage tags, and booking systems.
- There is no algorithmic conversion between the two systems — mapping requires lookup tables.
- US airports often follow the pattern K + IATA code (e.g., JFK → KJFK), but this rule does not apply globally.
- Small airfields may have only an ICAO code; some IATA codes exist for non-airport locations such as railway stations.
Sources & References#
- ICAO — Location Indicators (Doc 7910) — Official ICAO reference for four-letter aerodrome location indicators.
- ICAO — Designators for Aircraft Operating Agencies (Doc 8585) — Three-letter airline designator registry.
- FAA Aeronautical Information Manual (AIM) — Use of ICAO codes in flight plans, METARs, and ATC communications.
Related Guides#
Browse Directories#
- Airport Codes — Full reference of ICAO and IATA code systems, regional prefixes, and where codes appear.
More in Airports & Ground Operations#
Explore all guides in Airports & Ground Operations.