The IATA codes (which aren't always the same as the FAA codes) are used for ticketing purposes and the ICAO codes are used for ATC ops and making flight plans.

Many small airports in the US do not have ICAO codes, only FAA codes. For instance, Spruce Creek Airport in Florida is a famous fly-in community and it does not have an ICAO code but its FAA code is 7FL6. You enter it into the GPS or FMS of the aircraft the same way in the same place.

The only difference comes from filing a flight plan using an ICAO flight plan form. If the airport doesn't have an ICAO code, you enter a place-holder code ("ZZZZ") in the "departure" or "Destination" box and enter a specially-formatted tag in the remarks that looks like "DEST/7FL6."

FAA codes are used to identify fields generally from an administrative / budgeting perspective.

GalaxyFlyer wrote:

The FAA and ICAO codes are identical, IATA codes are for airline use, mostly ticketing.

GF

In the contiguous USA yes. In Alaska and Hawaii this is incorrect.

GalaxyFlyer wrote:

Correct, it’s the “P”, like the “K” that’s dropped. As in PHNL or PANC. Or PHIK or PMDY for two military instances.

GF

ICAO codes have a “wide geographic area (large country/Geographical portion of a continent)” indicated by the first letter, a “small geographic area(smaller country/part of a country)” indicated by the second letter, and a specific airport indicated by the last 2 letters. If a country is large enough to get its own first letter identifier, ie USA=K and China=Z, then the rest of the three letters can be whatever the country decides.

So CDG=LFPG, L is Lower europe (seams to cover Europe south of France, Switzerland Austria Slovakia), F is France, PG is Paris, de Gaul. LHR=EGLL, E=Europe (covering the UK, Germany, , G= Great Britain, LL=London Heathrow.


In the same vein, ICAO airport codes for airports in Hawaii start “PH” (Pacific, Hawaii). So For Maui/Kahului the ICAO code is PHOG, IATA is OGG, and the FAA code is OGG. Some airports are lucky enough that all codes line up (ICAO:PHNL, IATA:HNL, FAA:HNL). Similarly, all ICAO codes for Alaska start “PA” (Pacific, Alaska) - so Anchorage International is ICAO:PANC, IATA:ANC, FAA:ANC and Fairbanks is ICAO:PAFA, IATA:FAI, FAA:FAI.

The FAA computer system appears to take the FAA 3 letter IDs, which happen to match the ICAO codes (except in Alaska and Hawaii). The IATA codes are irrelevant from a flight plan perspective.

Carlsbad, CA is KCRQ/CLD. Truckee, CA is KTRK/TKF...exceptions to the convention. There are many others in the US.

26point2 wrote:

Carlsbad, CA is KCRQ/CLD. Truckee, CA is KTRK/TKF...exceptions to the convention. There are many others in the US.

KCRQ is CRQ with the FAA. CLD is the IATA code.

I would imagine that there is something to do with standards and licensing as well as private vs public use and what operations the airfield can be used for as well as insurance liabilites.
Can you buy a ticket to fly commercial there? IATA code
Can you fly in to it and does it have a certain standard for fire fighting capability can you use this for flight training etc. ICAO code
Is this Daves house and do you need specific permission from Dave to fly in there and does your insurance company need to allow you to do so? FAA code (people just need to know that that is where planes are going to be popping out of.

This is all half guessing and half memory from my eams 10 years ago for my PPL in the UK.

Fred

Every airport in the United States has a code assigned by the FAA. Not every airport in the US has an IATA code (if they don't have commercial airline service) or an ICAO code (if they don't have an ASOS/AWOS station or instrumental approach/navigation equipment/procedures).

Major airports have fully alphabetic codes; smaller GA-only airports have alphanumeric codes, and privately owned airfields have a four-character code that includes the postal abbreviation of the state the airport is located in plus two numbers, either before, after, or on either side of the state code (e.g. 26MI, 0MI9, MI42).

IATA codes, for the most part, are derived directly from the FAA codes. There have become exceptions to this rule, however, especially when cities relocate or replace their airports and the code changes, or if the FAA code otherwise changes only to conflict with an existing IATA code overseas.

The best example of this is Sawyer Airport in Marquette, MI, whose FAA code is SAW. The original Marquette County Airport used the code MQT, and when they closed the airport and moved into the former Sawyer Air Force Base, the IATA chose to keep the MQT designation instead of changing it to SAW as that was already the IATA code for an airport in Turkey.

Likewise, ICAO codes are also derived directly from FAA codes, amending a 'K' prefix. ICAO codes were created to establish a consistent, international standard for global navigation. In some cases, they correspond directly to the codes assigned by each country's aviation authority; in some cases they're completely different.

So, to answer your question: FAA codes are used for identifying ALL airports in the country, not just those served by commercial airlines or those with instrument procedures. They also serve all kinds of administrative purposes within the FAA itself. It may seem like they're kind of obsolete, but they're really not, as neither the IATA or ICAO have any direct authority to assign a code to the airport itself, they just identify them within their own systems.