ICAO vs IATA Airport Codes Explained

You book a flight to Los Angeles and see:

LAX

A flight plan for the same airport may use:

KLAX

Both identify Los Angeles International Airport.

But they belong to different systems.

And that is only the beginning.

Aviation also uses separate identifiers for:

• Airlines
• Flight numbers
• ATC callsigns
• Aircraft registrations
• Domestic airport identifiers
• Weather stations
• Cities and metropolitan areas

So the useful question is not simply: "Why does an airport have a three-letter code and a four-letter code?"

It is:

What exactly are we identifying, and which system is doing the identifying?

The Short Answer#

For a major commercial airport such as Los Angeles:

LAX is its IATA location identifier.

KLAX is its ICAO location indicator.

A useful beginner's shortcut is:

IATA → commercial/travel systems

ICAO → operational/aeronautical systems

That shortcut is useful.

It is not absolute.

The Aviation Identifier Stack#

Here is the bigger picture:

These identifiers answer completely different questions.

That distinction prevents most code-related confusion.

What Is an IATA Location Code?#

IATA, the International Air Transport Association, assigns three-letter location identifiers for commercial airline and travel-industry use.

For example:

These are the codes passengers encounter most often.

Where Are IATA Location Codes Used?#

Common uses include:

• Airline reservations
• Schedules
• Ticketing
• Boarding passes
• Baggage routing
• Airline websites
• Travel agencies
• Global travel-distribution systems
• Cargo systems

If your baggage tag says:

MAA

that is the commercial location identifier for Chennai.

See How Baggage Handling Works.

IATA Codes Do Not Only Identify Airports#

This is an important correction.

Calling every three-letter IATA location identifier an:

airport code

is convenient but incomplete.

IATA's current location database includes identifiers for:

• Airports
• Metropolitan areas
• Rail stations
• Bus stations
• Ferry ports
• Heliports
• Other intermodal locations

So the more precise term is:

IATA location identifier

or:

IATA location code

Airport codes are one major subset.

Metropolitan Area Codes#

Suppose one city is served by several airports.

A travel system may need a way to search:

the whole metropolitan area

rather than one specific airport.

IATA can therefore assign a city or metropolitan-area code.

For example, Washington, D.C. is served by airports including:

• DCA
• IAD
• BWI

IATA uses:

WAS

as the metropolitan-area code.

WAS does not identify one physical runway or airport.

It represents the wider Washington air-travel market.

One Code Can Represent Both City and Airport#

If one airport serves a metropolitan area, IATA can assign the same identifier to both the airport and city.

IATA gives Geneva as an example:

GVA

can represent Geneva Airport and the associated city in the applicable commercial context.

So even within the IATA system:

location code ≠ always one physical airport.

How Does IATA Choose the Letters?#

IATA's assignment rules aim for unique three-letter location identifiers.

When possible, a new code can be based on the location name.

That is why many are intuitive:

• SYD — Sydney
• DEL — Delhi
• SIN — Singapore

But availability and history matter.

Codes are not guaranteed to be the first three letters of the modern city name.

Historical Codes Can Outlive Names#

Mumbai still uses:

BOM

Chennai still uses:

MAA

Those codes make more sense when you remember the historical city names:

• Bombay
• Madras

Airport and city names can change far more easily than the global reservation systems built around their identifiers.

That is why old-looking codes often survive.

IATA Codes Are Intended to Be Stable#

IATA considers assigned location identifiers effectively permanent and says changes are rare.

That stability matters because codes become embedded in:

• Reservation systems
• Timetables
• Fares
• Baggage systems
• Historical data
• Airport systems
• Travel software

Changing three letters sounds easy.

Changing them across the global airline ecosystem is not.

But IATA Codes Can Change#

Rare does not mean impossible.

IATA cites Washington Dulles as a historical example.

Its identifier changed from:

DIA

to:

IAD

to reduce possible confusion with nearby Washington National's DCA.

So: "IATA codes never change"

is false.

A better statement is:

they are designed to be stable and are changed only infrequently.

What Is an ICAO Location Indicator?#

ICAO, the International Civil Aviation Organization, maintains a system of four-letter location indicators used across international aeronautical operations.

Examples include:

The relationship between the two columns is sometimes obvious.

Often it is not.

ICAO Calls Them Location Indicators#

"ICAO airport code" is common conversational language.

The more precise term is:

ICAO location indicator

That matters because ICAO's system is not limited to passenger airports.

Its official location-indicator publication covers geographical aeronautical locations more broadly.

National aeronautical-information publications can also contain location indicators for facilities other than airports.

For example, India's current AIP lists location indicators for aerodromes and facilities such as Flight Information Centres.

So:

four-letter ICAO location indicator ≠ necessarily a commercial airport.

Why Are ICAO Indicators Geographical?#

Unlike IATA codes, ICAO location indicators have a geographical structure.

Consider:

EGLL

for London Heathrow.

The beginning:

EG

places it inside the applicable ICAO location-indicator region.

The final characters identify the location within that framework.

Likewise:

LFPG

places Paris Charles de Gaulle within the applicable French indicator structure.

Do the First Two Letters Always Mean a Country?#

Not perfectly.

The common explanation: "first letter = continent, second letter = country"

is too simplistic.

ICAO's allocation system is geographical, but different regions use different structures.

Sometimes:

• One leading letter is highly significant.
• Two letters identify a national or regional block.
• States or territories use several prefix combinations.

Treat the prefix as a structured geographical allocation rather than a universal country-abbreviation formula.

The Continental U.S. K Pattern#

In the contiguous United States, a very useful pattern exists.

Many major airports have a domestic three-letter identifier.

Their ICAO location indicator is:

K + domestic identifier

Examples:

• LAX → KLAX
• JFK → KJFK
• ORD → KORD
• SEA → KSEA

This is why American IATA and ICAO airport identifiers can look unusually similar.

But do not turn that into: "Every U.S. airport is K + IATA."

That is not true.

Alaska Is Different#

Alaska uses ICAO prefixes including:

• PA
• PF
• PO
• PP

depending on the location assignment.

So an Alaskan airport might have an ICAO indicator such as:

PABE

rather than:

K...

The old statement: "Every U.S. airport starts with K"

fails immediately in Alaska.

Hawaii Is Different Too#

Hawaiian ICAO location indicators use:

PH

rather than K.

So Honolulu is not created by adding K to its passenger code.

This is another reason K + IATA should be taught as a contiguous-U.S. heuristic, not a U.S.-wide rule.

U.S. Territories Add More Exceptions#

Other U.S. jurisdictions use additional prefix systems.

For example, FAA material identifies:

• Puerto Rico — TJ
• U.S. Virgin Islands — TI

and Pacific locations use other allocated prefixes.

So ICAO geography follows international allocation structures, not simply political shorthand such as:

United States = K

Canada Is Not Simply C + IATA#

Another tempting shortcut is: "Canada uses C."

That is too crude.

Canadian ICAO station identifiers can use prefix groups including:

• CU
• CW
• CY
• CZ

A familiar airport example is:

YYZ → CYYZ

for Toronto Pearson.

Again, learn the geographic structure.

Do not try to generate identifiers from a one-letter country formula.

India Is a Great Example of Why Guessing Fails#

Indian operational identifiers illustrate the point particularly well.

Examples include:

• Delhi — VIDP
• Mumbai — VABB
• Chennai — VOMM

India's AIP organizes location indicators across its:

• Chennai FIR
• Delhi FIR
• Kolkata FIR
• Mumbai FIR

The prefixes therefore reflect an aeronautical geographical structure.

There is no simple rule such as:

V + IATA airport code

Delhi:

DEL → VIDP

Mumbai:

BOM → VABB

Chennai:

MAA → VOMM

You must look up the actual indicator.

Never Guess an ICAO Indicator From the IATA Code#

Sometimes this works:

ORD → KORD

Sometimes it clearly does not:

LHR → EGLL

CDG → LFPG

MAA → VOMM

The safe rule is:

look it up in the authoritative aeronautical data.

Does Every Airport Have Both Codes?#

No.

Large commercial airports commonly have:

• IATA location identifier
• ICAO location indicator

But there is no universal requirement that every landing facility have both.

A small aerodrome may have:

• National identifier
• ICAO indicator
• No IATA code

A very small or private facility may not have a standard ICAO location indicator either.

The coding systems serve different eligibility and operational purposes.

Why Might an Airport Have No IATA Code?#

IATA location identifiers exist for commercial airline and intermodal purposes.

If an airfield is not relevant to commercial airline distribution, there may be no reason for an airline or reservation system to request an IATA location code.

Examples can include:

• Small general-aviation fields
• Private airstrips
• Specialized facilities

So:

airport exists ≠ IATA code automatically exists

What If an Airport Has No ICAO Location Indicator?#

Flight-planning standards account for this.

In an ICAO-format flight plan, if a departure or destination does not have an assigned four-letter location indicator, the special entry:

ZZZZ

can be used.

The actual location is then specified elsewhere in the flight-plan information.

In U.S. filing, FAA guidance similarly provides procedures for non-ICAO airports using ZZZZ and the applicable domestic identifier.

So:

no ICAO indicator does not mean the location cannot be used.

The United States Has a Third System: FAA Location Identifiers#

The U.S. adds another layer.

The FAA maintains its own location identifiers for domestic aeronautical use.

Major airports often make the system look simple.

For example:

SEA

can be the U.S. domestic location identifier, while:

KSEA

is the corresponding ICAO station identifier.

But smaller facilities can have identifiers containing:

• Letters
• Numbers

and may not have an IATA passenger code at all.

FAA LID Is Not the Same Thing as IATA#

This distinction is easy to miss because at many major U.S. airports the same three letters happen to be used.

For example:

ORD

works as O'Hare's familiar IATA airport code and domestic identifier.

But:

IATA and FAA are different authorities maintaining different identifier systems.

Matching text does not make them the same namespace.

The FAA System Includes More Than Airports#

FAA Order JO 7350.9 covers identifiers for many aeronautical facilities, including categories such as:

• Airports
• NAVAIDs
• Weather stations
• Fixes and procedures

That is another reason the generic phrase:

airport code

can hide important distinctions.

Where ICAO Location Indicators Appear#

Four-letter location indicators are widely used in operational aviation, including:

• Flight plans
• Aeronautical information
• Weather products
• Some NOTAM contexts
• Dispatch systems
• Navigation databases

But saying: "pilots use ICAO airport codes for everything"

would still be wrong.

Flight Plans#

For an ICAO-format flight plan, departure and destination aerodromes are normally identified using the appropriate four-letter location indicator.

For example:

KLAX

rather than:

LAX

when the ICAO location indicator is required.

If no indicator exists, procedures such as ZZZZ are available.

See Flight Plan.

METARs#

A METAR uses a four-letter ICAO station identifier.

A report might begin:

METAR KJFK ...

Notice something important:

KJFK is not necessarily the first token.

The report type:

METAR

or:

SPECI

appears first in standard reports.

The station identifier follows.

See How to Read a METAR.

TAFs#

A TAF likewise uses the applicable four-letter station/location identifier for the forecast location.

For example:

TAF KJFK ...

See How to Read a TAF.

NOTAMs and Aeronautical Information#

ICAO location indicators are also embedded throughout the operational aeronautical-information ecosystem.

That includes material involving:

NOTAMs

and national Aeronautical Information Publications.

But actual NOTAM and AIS formats can contain additional identifiers and conventions.

It is better to understand ICAO location indicators as part of the operational data system than to assume every technical message consists solely of four-letter airport codes.

Do Pilots Say "KJFK" on the Radio?#

Usually not as the aircraft's callsign.

This is one of the biggest missing distinctions in the old explanation.

ATC communication uses aircraft callsigns.

Airport location indicators and aircraft callsigns are different identifier systems.

Airport Identifier Versus Aircraft Callsign#

Suppose an American Airlines flight is heading to JFK.

The destination can be identified operationally as:

KJFK

The airline itself can be identified operationally as:

AAL

The airline's telephony designator is:

AMERICAN

These identify entirely different things.

IATA Airline Designator#

Airlines also have commercial IATA designators.

American Airlines uses:

AA

These codes are used in areas such as:

• Reservations
• Schedules
• Ticketing
• Timetables
• Commercial systems

IATA airline designators are typically two characters, and the system can include digits.

So:

IATA airport/location code = three characters

does not mean:

all IATA codes are three characters.

ICAO Airline Designator#

ICAO maintains a separate three-letter system for aircraft operating agencies.

American Airlines uses:

AAL

This is an ICAO airline/company designator.

It is not an airport code.

That matters because both:

LAX

and:

AAL

contain three letters.

But:

• LAX = IATA location
• AAL = ICAO airline/operator designator

Length alone does not tell you what namespace you are looking at.

Telephony Designator#

ICAO also maintains telephony designators used in spoken ATC communication.

For American Airlines:

AAL is the three-letter company designator.

AMERICAN is the telephony designator.

So an airline flight can have several representations depending on context.

One Airline Flight, Several Identifiers#

Imagine American Airlines Flight 100.

Commercially, you might see:

AA100

Operational systems can identify it using:

AAL100

On the radio, the airline portion is spoken using the telephony designator:

AMERICAN

This is why saying: "ICAO airport codes are what pilots use on the radio"

is misleading.

ATC aircraft identification is its own system.

Flight Number Is Yet Another Identifier#

A flight code normally combines:

airline designator + flight number

such as:

AA100

The AA identifies the airline commercially.

The 100 identifies the scheduled service within that airline's system.

That is different from:

JFK

which identifies a location.

Flight Number Versus Airport Code#

Compare:

AA100

and:

JFK

One describes:

an airline service

The other describes:

a location

They are not variants of the same coding system.

Flight Number Versus Aircraft Registration#

A flight number identifies a scheduled service.

An aircraft registration identifies a physical aircraft.

The same flight number can be operated by:

• Different aircraft on different days
• A replacement aircraft after a swap
• Sometimes a different operating carrier under an applicable partnership

Meanwhile one physical aircraft operates many different flight numbers during its working life.

So:

flight number ≠ aircraft identity

Registration Versus Callsign#

General-aviation aircraft often use their registration as part of their ATC identification.

Airline aircraft commonly use company/telephony designators plus flight identification.

This is why:

callsign

and:

registration

can sometimes be closely related but are still conceptually different.

Codeshares Add Another Flight Number Layer#

A codeshare flight can have:

• Operating flight number
• One or more marketing flight numbers

See Codeshare Flights Explained.

For example, one physical operation might appear commercially under:

Airline A 123

and:

Airline B 4567

while the airport itself still has its own unrelated:

• IATA location identifier
• ICAO location indicator

Do not confuse:

airline code

with:

airport code

simply because both appear on the same itinerary.

Codeshare Example: Four Different Identities#

A codeshare booking can therefore contain four separate identity layers:

1. Airport — LHR
2. Marketing airline — commercial airline designator
3. Operating airline — actual carrier
4. Flight number — scheduled service

Operational systems may then use:

5. ICAO location indicator — EGLL
6. ICAO airline designator
7. Telephony callsign
8. Aircraft registration

Aviation does not have one universal code because it is identifying many different objects.

IATA Versus ICAO: Better Comparison#

The last two rows are particularly important.

"Passengers vs Pilots" Is a Shortcut, Not a Rule#

You will often hear: "IATA is for passengers; ICAO is for pilots."

As a beginner's memory aid, that is useful.

A better version is:

IATA location identifiers are primarily commercial.

ICAO location indicators are primarily operational.

Why the caveat?

Because airlines themselves use IATA codes throughout serious backend:

• Scheduling
• Cargo
• Revenue
• Distribution
• Baggage

systems.

Likewise, passengers can encounter ICAO identifiers in:

• Flight trackers
• Weather apps
• Aviation websites

The difference is function, not whether a passenger is physically allowed to see the code.

IATA Airport Codes on Baggage#

Your bag needs to be routed commercially through the airline network.

That is why familiar three-letter location identifiers are heavily used in baggage processes.

A tag might route your bag through:

MAA → DXB → LHR

Those are IATA location identifiers.

See How Baggage Handling Works.

ICAO Indicators in Weather#

Weather systems need an operational station identity.

For a major U.S. airport:

JFK might be the familiar passenger code.

The weather station identifier is:

KJFK

That distinction becomes immediately useful when reading aviation weather.

What About Airport Departure Boards?#

Passenger-facing departure and arrival systems normally emphasize:

• City
• Airport name
• IATA location identifier

because that is the identifier passengers recognize.

Operational systems behind the scenes can use different identifiers simultaneously.

One screen saying:

LHR

does not mean the airline's dispatch system has stopped using:

EGLL

where appropriate.

Airport Name Versus Airport Code#

Airport names can change while codes remain stable.

That is intentional.

Codes are identifiers.

They are not required to be perfect abbreviations of today's marketing name.

This explains apparently strange combinations around the world.

ORD Is a Famous Example#

Chicago O'Hare uses:

ORD

rather than something obvious like:

OHA

The code reflects the airport's historical association with Orchard Field.

That illustrates a useful principle:

airport codes preserve history.

Do not assume the letters must match the modern airport name.

MAA and BOM Make the Same Point#

Chennai uses:

MAA

Mumbai uses:

BOM

Their commercial codes preserve identifiers rooted in the older names:

• Madras
• Bombay

This is not an error.

The stability of the code is often more valuable than making it cosmetically match a renamed city.

Can Different Terminals Have Different Airport Codes?#

Normally:

no

Terminal 1 and Terminal 2 are parts of one airport.

They share that airport's identifiers.

But a metropolitan area can contain several separate airports, each with its own airport code.

For example, the Washington area includes:

• DCA
• IAD
• BWI

while:

WAS

can represent the metropolitan area in IATA systems.

Airport Versus Metropolitan Area#

This creates an important booking distinction.

Searching:

IAD

means:

Washington Dulles specifically.

Searching:

WAS

can mean:

the broader Washington metropolitan market.

That is why location codes should not automatically be interpreted as:

a set of runways.

How Should You Look Up a Code?#

Use the source appropriate to the namespace.

IATA location identifier#

Use IATA's official airline/airport code search or its Airport & Location Identifier Database.

ICAO location indicator#

Use current national aeronautical information and ICAO Doc 7910.

U.S. domestic identifier#

Use FAA aeronautical data and FAA Order JO 7350.9.

ICAO airline and telephony designator#

Use ICAO Doc 8585 or the relevant official aeronautical designator data.

Guessing from memory is fine for trivia.

It is not a good operational method.

Common Myths About IATA and ICAO Codes#

Myth: Every airport has an IATA and ICAO code#

No.

Different facilities qualify for different identifier systems.

Some have both.

Some have only operational or national identifiers.

Myth: IATA codes only identify airports#

No.

IATA also assigns location identifiers to metropolitan areas and eligible intermodal locations such as railway, bus and ferry facilities.

Myth: ICAO four-letter indicators only identify airports#

No.

They belong to a broader aeronautical location-indicator system.

Myth: IATA is for passengers and ICAO is for pilots#

That is a useful beginner shortcut, but too absolute.

A better distinction is:

commercial versus operational emphasis.

Myth: ICAO is simply IATA with one extra letter#

No.

ORD → KORD happens to work.

LHR → EGLL does not.

MAA → VOMM does not.

Myth: Every U.S. ICAO airport indicator starts with K#

No.

K applies to the familiar contiguous-U.S. pattern.

Alaska, Hawaii, Puerto Rico and other U.S. jurisdictions use other ICAO prefixes.

Myth: Canada is simply C + IATA#

No.

Canadian station identifiers use several ICAO prefix groups, including CY, CW, CU and CZ.

Myth: ICAO airport codes are spoken in every ATC radio call#

No.

Aircraft use callsigns.

ICAO location indicators identify locations.

ICAO also maintains separate three-letter airline and telephony designators for aircraft identification.

Myth: Flight number and callsign are the same thing#

They can be closely related for airline operations but belong to different operational/commercial representations.

Myth: Flight number identifies the aircraft#

No.

A flight number identifies a service.

An aircraft registration identifies the physical aircraft.

Myth: Three letters always mean an airport#

No.

LAX is an IATA location identifier.

AAL is an ICAO airline designator.

Context determines the namespace.

Myth: Airport codes never change#

They are deliberately stable, especially in commercial systems, but changes can occur.

Myth: A renamed city must get a new airport code#

No.

BOM and MAA demonstrate how historical codes can remain after city names change.

Myth: METARs begin with the airport code#

A standard METAR begins with the report type, such as METAR or SPECI, followed by the four-letter station identifier.

Myth: If an airport has no ICAO code, you cannot file a flight plan to it#

No.

ICAO-format filing provides procedures such as ZZZZ to identify aerodromes without an assigned four-letter location indicator.

Frequently Asked Questions#

Key Takeaways#

• IATA and ICAO maintain different location-identification systems for different purposes.
• IATA uses three-letter location identifiers primarily across commercial airline and travel systems.
• ICAO uses four-letter location indicators primarily across operational aeronautical systems.
• "IATA airport code" and "ICAO airport code" are useful shorthand, but "IATA location identifier" and "ICAO location indicator" are more precise.
• IATA location identifiers do not only represent airports.
• IATA also codes metropolitan areas and eligible rail, bus, ferry, heliport and other intermodal locations.
• WAS is an IATA metropolitan-area code; DCA, IAD and BWI identify individual airports in the Washington area.
• IATA codes often resemble location names but can preserve historical names.
• BOM and MAA remain useful examples of commercial codes outliving city-name changes.
• IATA location identifiers are intended to be stable and are changed only infrequently.
• ICAO location indicators are geographically structured.
• The geographical prefix should not be reduced to a universal "country abbreviation" rule.
• In the contiguous United States, many three-letter domestic identifiers form an ICAO indicator by adding K.
• The K pattern does not apply to every U.S. location.
• Alaska, Hawaii, Puerto Rico and other U.S. jurisdictions use different ICAO prefix groups.
• Canada cannot be safely reduced to "C + IATA."
• Delhi uses DEL/VIDP, Mumbai BOM/VABB and Chennai MAA/VOMM, showing why ICAO indicators should not be guessed from IATA codes.
• Not every airport has both an IATA and ICAO identifier.
• The FAA maintains a separate U.S. domestic location-identifier system.
• FAA location identifiers and IATA codes are separate namespaces even when the text happens to match.
• Some U.S. facilities use alphanumeric FAA identifiers and have no IATA code.
• ICAO flight plans normally use four-letter location indicators for aerodromes that have them.
• ZZZZ provides a mechanism for flight-plan locations without an assigned ICAO indicator.
• METARs and TAFs use four-letter ICAO station/location identifiers.
• A standard METAR begins with its report type before the station identifier.
• Airport location indicators are not the same thing as ATC aircraft callsigns.
• Airlines have separate IATA commercial designators, ICAO three-letter designators and ICAO telephony designators.
• American Airlines is a useful example: AA is the IATA designator, AAL the ICAO designator and AMERICAN the telephony designator.
• A flight number identifies a service; it does not identify an airport.
• An aircraft registration identifies the physical aircraft; it is not the same thing as a flight number.
• Codeshares can create several marketing flight numbers for one physical operation without changing the airport identifiers involved.
• Three letters do not automatically mean "airport": namespace and context matter.
• The most useful beginner shortcut is IATA = commercial emphasis and ICAO = operational emphasis, with important exceptions.
• Operationally, identifiers should be looked up from authoritative current data rather than inferred from patterns.

Sources & References#

• ICAO Doc 7910/200, Location Indicators, 200th Edition, June 2026 — current ICAO four-letter location-indicator reference and corresponding IATA identifiers where available.
• ICAO Doc 8585/217, Designators for Aircraft Operating Agencies, Aeronautical Authorities and Services, 217th Edition, July 2026 — ICAO three-letter aircraft-operator and telephony designators.
• IATA, Airport & Location Identifier Database — current official IATA database for airports, metropolitan areas and intermodal location identifiers.
• IATA, IATA Location Codes and Resolution 763 guidance — assignment, metropolitan-area, intermodal, history and code-change principles.
• IATA, Airline Coding Database — current commercial airline designators and related coding data.
• FAA Order JO 7350.9GG, Location Identifiers — current U.S. domestic aeronautical location-identifier reference.
• FAA Aeronautical Information Manual — ICAO flight-plan location identifiers, non-ICAO aerodrome handling and METAR station-identifier conventions.
• FAA, ICAO Aircraft Company Three-Letter Identifier and/or Telephony Designator Assignments — U.S./ICAO airline designator and radio telephony reference.
• FAA Chart Supplement — current U.S. airport and aeronautical facility publication formerly commonly known as the Airport/Facility Directory.
• Airports Authority of India, current eAIP GEN 2.4 — Indian ICAO location indicators and FIR-based location listings.
• Aviatopia: Codeshare Flights Explained, How Airlines and Airports Work, Airport Operations 101, How Baggage Handling Works, How to Read a METAR, and How to Read a TAF.