The IATA code is three letters and is used in direction finders and ticket purchasing sites on the internet. The ICAO code is a four letter cipher, and is used more for international dealings and other flight related tasks.

The IATA abbreviation stands for the International Air Transport Association. The airport codes distributed by the IATA are used by them everywhere, especially to mark luggage and find airline seats.

The codes are issued by the IATA headquarters in Montreal, and are published biannually in the IATA coding directory. After being issued, all airports are given a unique three letter cryptogram.

Codes that are defunct for any reason may be used again at a later date for some other airport, after a suitable time period has passed. These codes are highly useful for security, air cargo tracking, and for international transfers.

If an airport does not have their own code because they are too small, then they are given a Location Identifier instead. The IATA also issues codes for railways.

IACO stands for the International Civil Aviation Organization. The IACO issues four letter codes to each of them. The main focus for these ciphers is with international transport and travel. The IACO airport code for each of them gets issued through the ICAO Document 7910: Location Indicators.

They are used for air traffic control, flight planning and air cargo tracking, rather than for the general public. The IATA code for Heathrow airport is LHR, but the ICAO code is EGLL. IACO codes are broken down by regions, and that is how they get their names.

In most cases, the first letter stands for the continent or region, the second letter stands for the country, and the third and fourth letters stand for the name of the specific airport. For airports with no IACO codes, if needed, the fake code of ZZZZ can be temporarily used.

Both the IATA and ICAO airline codes are used to identify airports. However, each airport code is significant to a specific airdrome.

The IATA codes are used for things such as baggage transfers between airports and for reserving airline seats, and the ICAO codes are used for things such as flight plans and transport information. With either code, it is nice to know that the airports have you covered.