Early in flight training, pilots learn that airports we go to have a 3 character FAA (Federal Aviation Administration) identifier. My home airport is EMT and pilots soon go to POC. The terminal chart (TAC), sectional chart, chart supplement, or your favorite app or airport information web site will all show this identifier

You might think… Great! I can use that FAA identifier in all my apps, tools, and web sites. Students quickly realize that’s not true. The US government’s own aviationweather.gov site will give you a “No METAR found for EMT” error, but works if you enter KEMT. So, great, I just have to use that second identifier. Not so fast! You quickly realize that not all airports have that second identifier. Take as an example the Big Bear City Airport, with the identifier of L35:

There is no second identifier listed and aviationweather.gov gives you the “No METAR found for L35”. So, being the fast learner that you are, you try KL35 and find it works! Great, just throw a K in front of the FAA identifier and all is well. Eh… if only it were so simple. Put KL35 in a Garmin 430 navigator and it won’t work. Put EMT in that same navigator and it won’t work either. It is unfortunately (as you should be guessing by now) not as simple as you would like it to be. Are we left with just randomly trying with and without a K? That will almost work, but can end up with confusion when you realize that the Garmin GPS is taking you not to center of the airport when you enter VNY as your destination. Time to step back and try to make a little more sense of what’s going on.

Now, my discussion is aimed primarily at students and pilots flying in the “lower 48″/CONUS (CONtiguous United States), but hopefully will be of use to others who run into similar confusions in other parts of the US or even the world.

FAA Identifier

The FAA assigns a location identifier to all airports in the US. For “major” airports, this will be a 3 letter identifier, such as EMT, LAX (Los Angeles International), or AJO (Corona Municipal). We’ll ignore for now that my examples include a non-towered airport and a Class B airport. For smaller public use airports, you’ll usually see a combination of 1 letter and 2 digits, like L35, F70, or 8S2. For private airports, you’ll most often see combinations of 2 letters and 2 numbers – 3CL4 is the Pasadena Police Heliport near me and the Halter Ranch Airport near Paso Robles is 89CA. Some of the identifiers have other info buried inside them, such as 89CA showing it is in California (but that’s more of a guideline than a rule). 3 letter airports that start with N are intended to be assigned to Department of Defense (military) airports like NID (China Lake Naval Air Weapons Station) or NKX (Marine Corps Air Station Miramar). Most aviation oriented navigation systems will know about the airports that are assigned 3 character identifiers, but fewer will be aware of the 4 character ones. While the Sectional chart shows the location of Halter Ranch, it does not give the identifier.

ICAO Identifiers

Those FAA identifiers are not unique throughout the world though and many of the apps, tools, and sites we use are designed to be used internationally. The ICAO (International Civil Aviation Organization) is the agency of the United Nations responsible for many of the standards for aviation across national boundaries. That KEMT we saw earlier is the ICAO identifier for El Monte (actually now San Gabriel Valley) Airport. That example should show you that sometimes the letters make sense for the name of the airport and sometimes they don’t. In the assignment of ICAO airport identifiers, the first letter or two tells you something about either the geographic or political affiliation of the airport. K says that the airport is in the contiguous United States! Now, ICAO codes only allow letters so KL35 is not a valid ICAO code and indeed Big Bear does not have an ICAO airport code. So, what about Hawaii and Alaska? They have ICAO codes that start with PH and PA respectively, so that the main airport in Anchorage is ANC for its FAA identifier and PANC for ICAO; Honolulu is HNL and PHNL (many smaller airports take the first two letters of the FAA and append to PA or PH – OME and PAOM for Nome, AK).

[Note: I have seen some lists of ICAO airport codes that include numbers, but the ones I’ve tracked down seemed to have been in error, but I make no guarantees]

OK, so why did aviationweather.gov want KL35 when you just told me that isn’t a valid ICAO airport code? Because aviationweather.gov may look like it is using airport codes, but it isn’t really…

NWS Station Identifiers

The National Weather Service (NWS) that runs aviationweather.gov and provides much of the weather information and forecasts that we all use every day has a related, but different set of weather station identifiers. For the airports that have ATIS, AWOS or ASOS systems that feed the METAR system in the CONUS, the NWS station identifier is indeed a 4 character identifier that starts with K and includes the FAA identifier. You can see a list of these NWS identifiers. But not everything that is an NWS identifier is an airport. Pilots in SoCal will quickly recognize the location and ICAO identifiers of all these local airports in a plot of METARs from aviationweather.gov:

That is until you realize there is no airport KCQT or CQT in that area near the intersection of I-10 and I-110 by downtown LA. That weather station has all the capabilities of an airport weather station, but is the NWS weather station for Downtown LA on the USC campus. If you hear some news report on the current “LA Weather”, that is usually where they are getting that weather information. So, not everything that looks like a valid ICAO airport code is actually an airport code.

VOR identifiers

Now, let’s add to the confusion just a bit more before we try to boil it all down. Many airports have a VOR (a type of navigational transmitter) somewhere around the airport. LAX is a perfect example. LAX is the FAA identifier for the airport and KLAX is the ICAO identifier for the airport. But, LAX is also the identifier for the VOR (and LAX will be transmitted over the VOR’s audio in morse code to identify it). If you put LAX as a waypoint into Foreflight or most other navigational apps, you will be directed to the LAX VOR, but if you enter KLAX you’ll be taken to the center of the airport runway complex; LAX and KLAX are separated by 1.3 nautical miles!

Boiling it down

For most apps (e.g., Foreflight) and panel mounted GPS units (Garmin 430) when operating in the contiguous US :

• Enter the ICAO airport code if there is one (i.e. if the FAA code is 3 letters, add a K to get the airport) – KEMT instead of EMT
• Enter the FAA code if the airport has numbers in it – L35 not KL35
• Enter the VOR identifier to get the VOR as a waypoint instead of the airport – LAX for the VOR, KLAX for the airport, If you enter 3 letters that don’t match to a VOR but do match to an airport, apps like Foreflight will assume you mean the airport – foreflight will change EMT to KEMT in this case.

For aviationweather.gov (and possibly other aviation weather sites), enter the NWS station code, which will usually be K+FAA airport identifier, so KL35 instead of L35 and KEMT instead of EMT.

If L35 doesn’t work someplace, try KL35. If KL35 doesn’t work someplace, try L35 🙂

IATA and other codes – muddying the waters more

If the existence of both FAA and ICAO airport identifiers isn’t enough, there’s another airport identifier system you may encounter – IATA (International Air Transport Association) identifiers. If you fly commercially, you’ll find these codes on your tagged baggage. These are a different set of 3 character identifiers. For many major US airports, it’s easy: LAX is the FAA and IATA code and KLAX for ICAO, SFO/SFO/KSFO, ORD/ORD/KORD. But internationally it often is confusing – Heathrow is ICAO of EGLL and IATA of LHR (which makes more sense). There are some US airports that don’t have ICAO codes but do seem to have IATA codes. RBF is the code for Big Bear (L35 FAA), but as noted before it has no ICAO code. Luckily, I have not run into any needs to use IATA codes as a small aircraft instructor.

Now, I should also mention that there are many other things that look like ICAO codes that are neither weather stations nor airports. KABC can refer to both a radio station and tv station in LA. K for US radio stations has been used for radio and TV station in the western US.

There are also some 3 and 4 letter codes used in aviation that are not airports or VORs. The ARTCC (Air Route Traffic Control Centers) are given 3 letter identifiers that start with Z – ZLA refers to “Los Angeles Center” and ZKC refers to “Kansas City Center”. You may deal with controllers in these centers when getting flight following or while IFR outside of approach control areas There are 22 ARTCCs in the US. For international reference to those ARTCCs, you’ll see them identified such as KZLA (which is also the ID for a radio station in LA). B17 might look like a valid FAA airport identifier, but is actually an Aircraft Type Designator (like C172 or B737) for a Boeing B-17 Flying Fortress bomber (luckily, B17 is not a valid airport identifier).

If you find other weird areas for confusion on aviation identifiers, let me know.