What Do Airport Identifier Codes Mean? Decoding KJFK, JFK, and Everything In Between

Airport identifier codes are the short letter-and-number tags that uniquely name an airport so pilots, controllers, and computers all point to the same field. There are three systems you will meet: the FAA location identifier, the four-letter ICAO code used for flight planning and weather, and the three-letter IATA code printed on your luggage tag. Each one was built for a different job.

If you have ever wondered why your home field shows up as “LAX” on a boarding pass but “KLAX” in a weather report, you are seeing two different naming systems pointed at the same runway. It confuses brand-new students more than almost anything else on the chart, because nobody sits you down and explains that an airport can wear three different name tags at once. This guide untangles all three systems the way I walk a primary student through it in the cockpit, so the next time you file a flight plan or pull a METAR, the letters actually mean something.

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What is an airport identifier code?

An airport identifier code is a short, unique tag, made of letters or letters and numbers, that names one specific airport so that pilots, air traffic control, weather systems, and flight-planning computers all refer to the same field without ambiguity. Instead of typing out “John F. Kennedy International Airport,” everyone uses a code, and the code points to exactly one place on Earth.

The reason codes exist at all is uniqueness. There are tens of thousands of airports worldwide and plenty of duplicate names, so a system that guarantees one tag points to one field is essential. When you file a flight plan, request a weather briefing, or program a GPS, you are speaking in identifiers, not full names. Learning to read them fluently is part of learning to read the entire aeronautical information system.

The wrinkle that trips up students is that a single airport can carry more than one identifier at the same time, because different organizations built different systems for different purposes. That is what the next section sorts out.

What is the difference between ICAO, IATA, and FAA codes?

There are three identifier systems, and each was built by a different organization for a different job. ICAO codes are four letters and are used for aviation operations: flight plans, ATC, NOTAMs, and weather products. IATA codes are three letters and are used commercially for tickets, baggage, and airline schedules. FAA location identifiers are three or four characters that the FAA assigns to US airports, navaids, and fixes. They overlap but are not interchangeable.

The International Civil Aviation Organization (ICAO) assigns four-letter codes that are globally unique and structured by region, published in ICAO Document 7910. These are the codes a pilot lives in: KJFK, EGLL (London Heathrow), PANC (Anchorage). When you pull a METAR or file IFR, you are using ICAO.

The International Air Transport Association (IATA) assigns the three-letter codes that the traveling public sees: JFK, LHR, ANC. These are optimized for airline reservation systems and the bag tag on your suitcase, not for cockpit operations. Many small airports that never see an airliner have no IATA code at all.

The Federal Aviation Administration (FAA) maintains its own location identifiers for the US system, published in FAA Order JO 7350. An FAA ident can be a clean three-letter code that matches the IATA code, or it can be an alphanumeric mix like 7S5 or 2W6 for fields too small to rate a letters-only code.

Why do US airports start with the letter K?

US airports in the contiguous 48 states start with K because ICAO divides the world into regions and assigns each a prefix letter, and the United States was given the “K” block for its lower-48 airports. So the four-letter ICAO code is usually just the familiar three-letter identifier with a K bolted onto the front: LAX becomes KLAX, ORD becomes KORD, DEN becomes KDEN.

The prefix is regional, not random. The contiguous US uses K, Alaska uses PA, and Hawaii uses PH (with the remaining letters making up the rest of the four-character code, like PANC for Anchorage and PHNL for Honolulu). Cross an ocean and the pattern continues: Canada uses C, the United Kingdom uses EG, and so on. Once you know your region’s prefix, a four-letter ICAO code decodes itself.

One caution: the tidy “add a K” rule only works cleanly when the airport already has a three-letter ICAO-compatible identifier. Plenty of small US fields have an FAA ident with a number in it, and those do not get a simple K prefix, which is exactly why students get tangled up.

What do the letters in an airport code actually stand for?

Most of the time, the letters are an abbreviation of the airport or city name, but plenty of codes are historical leftovers that no longer obviously connect to anything. There is no requirement that an identifier spell out the airport’s current name, the code only has to be unique, so the letters range from obvious (BOS for Boston) to baffling (ORD for Chicago O’Hare).

The famous example is ORD, Chicago O’Hare. The field was originally Orchard Field, the airport was renamed for war hero Edward “Butch” O’Hare, but the identifier kept its “OR-D” roots. LAX is another: when codes expanded from two letters to three in the 1940s, many airports simply added an X to their old two-letter code, so “LA” became “LAX.” Once you know the letters are often frozen history rather than a live abbreviation, you stop trying to force every code to make sense.

For a student pilot, the practical takeaway is this: do not memorize codes by guessing the spelling. Look the airport up, confirm the identifier in an official source, and use exactly what is published. Treating a code as a fixed label rather than a puzzle to solve keeps you out of trouble on a flight plan.

Which airport code do pilots actually use?

For flying, you use the ICAO four-letter code in nearly every operational context: filing a flight plan, requesting a weather briefing, reading a METAR or TAF, checking NOTAMs, and programming most GPS and flight-planning systems. The three-letter IATA code is for the airline and travel world; it rarely appears in the documents a pilot works from.

Here is where it bites new pilots. You pull up the weather for your destination and the report is headed “KSLC,” but the airport’s sign and the chart legend you half-remember said “SLC.” Same airport, different system. METARs, TAFs, and most aviation weather use the ICAO code, so for the contiguous US you will almost always be reading a four-letter code that begins with K. Flight planning apps will frequently accept either the FAA ident or the full ICAO code, but the moment you talk to the official system, think ICAO.

Want a clear, beginner-friendly walkthrough of charts, weather, and flight planning before your first solo cross-country? Our free Total Student Pilot course teaches the whole aeronautical information system in the same plain-English style you are reading right now, so the codes, charts, and weather products stop looking like alphabet soup.

Why do some small airports have numbers in their codes?

Small US airports often have numbers in their identifiers because the FAA ran low on clean three-letter combinations and started issuing alphanumeric location identifiers to lower-traffic fields. A code like 7S5, S43, or 2W6 is a perfectly valid FAA location identifier, it just signals a smaller airport that does not have, and usually does not need, an ICAO or IATA code.

These alphanumeric idents are extremely common at the kind of fields where a lot of private-pilot training happens, backcountry strips, grass runways, and small municipal airports. Because they contain numbers, they break the “add a K for the ICAO code” rule entirely; many of these airports simply have no ICAO code at all. When you flight-plan to one, you use the FAA identifier exactly as published in the Chart Supplement, and you confirm whether your weather and filing tools recognize it before you depend on it.

This is the single most common point of confusion I see in primary students: they assume every airport has a four-letter “real” code. It does not. The FAA identifier is the real, official name for thousands of small US airports, numbers and all.

A real moment from the cockpit: I had a student up here in Alaska planning his first cross-country in the 172, and he sat there for a solid minute trying to type a leading “K” in front of a little strip’s identifier because his app would not accept the number-letter code he was reading off the chart. He was convinced he had the wrong ident. I reached over, deleted the K, and said, “That number-letter code IS the airport’s real name, the K rule only works when there is a clean three-letter code underneath.” His shoulders dropped, the flight plan filed, and we flew. Up here half the fields I teach out of carry an alphanumeric FAA ident and nothing else, so I drill it early: read what is published, file what is published.

Where do you look up an airport’s identifier?

You look up an airport’s identifier and its full data in the Chart Supplement U.S., the FAA publication formerly called the Airport/Facility Directory. Every public-use US airport has an entry that lists its identifier, runways, frequencies, lighting, services, and remarks, all keyed to that identifier. Modern flight-planning apps pull from the same FAA data, so the identifier you see in the app traces back to the official source.

The Chart Supplement is the authoritative reference, and reading it is a tested skill. On the FAA Private Pilot knowledge exam, interpreting Chart Supplement entries is PLT078 and recalling that information is PLT281. The supplement is published in regional volumes and updated on the 56-day cycle, so always work from current data rather than a printout from last year.

A practical habit worth building early: when you brief any unfamiliar field, find it in the Chart Supplement (or your app’s airport page, which mirrors it), confirm the identifier, and note whether it carries an ICAO code or only an FAA ident. That five-second check tells you exactly how to file and how to pull weather for the place.

Airport code systems compared

Here is the whole picture in one place. Notice how the same airport, Los Angeles, wears three different tags depending on who is using it.

The takeaway: a major airport may have all three codes pointing at it, while a small grass strip may have only an FAA identifier. As a pilot, the ICAO and FAA codes are the ones that matter operationally.

PLT Study Guide

The FAA tags Private Pilot knowledge-test questions with PLT (Pilot Learning Statement) codes. Airport identifier codes live in the Chart Supplement, so the two relevant codes both point there:

• PLT078 — Interpret information in a Chart Supplements U.S. This is the core code for airport identifiers. Expect questions that hand you a Chart Supplement entry and ask you to read the identifier, frequencies, runway data, or services for a specific field.
• PLT281 — Recall information in a Chart Supplements U.S. The recall counterpart, testing whether you know what kind of information the Chart Supplement contains and how it is organized, including how airports are listed by identifier.

Study the canonical sources behind these codes: the Chart Supplement U.S. itself (read several real entries until the layout stops looking busy), Chapter 14 (Airport Operations) of the Pilot’s Handbook of Aeronautical Knowledge (FAA-H-8083-25C), which is where the handbook walks through the Chart Supplement, and FAA Order JO 7350 for the location-identifier system. If you can find any US airport in the Chart Supplement and read its identifier and data cold, you have these PLT codes handled.

Frequently Asked Questions

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FROM CHRIS

Airport identifier codes stop feeling like a random pile of letters once you see the structure: three systems, each built for a different job, sometimes stacked on the same airport. Learn that ICAO four-letter codes are what you fly with, IATA three-letter codes are what travelers see, and FAA identifiers are the official US names, numbers and all, and you will read any chart, weather report, or flight plan with confidence.

Throttle On!

Chris Palmer

Founder & Chief CFI, Angle of Attack — Two-Time Master Aviation Educator and Gold Seal CFI