Two Airports, Same Code. How Aviation Handles This Mess

It shouldn’t happen—each airport should have a unique identifier. Yet multiple airports sometimes share codes, whether through historical accident, administrative overlap, or system limitations. Understanding how aviation handles these rare duplications reveals how the industry manages ambiguity in systems that can’t afford confusion.

The Two-Code System Helps

Commercial aviation operates with two parallel code systems that provide built-in redundancy against confusion.

IATA codes: Three-letter codes used for ticketing, baggage handling, and passenger-facing operations. LAX, JFK, ORD. These are administered by the International Air Transport Association.

ICAO codes: Four-letter codes used by pilots and air traffic control. KLAX, KJFK, KORD for U.S. airports. These are administered by the International Civil Aviation Organization.

Built-in disambiguation: Because the systems are independent, duplicate IATA codes can have different ICAO codes. When ambiguity exists in one system, the other system resolves it.

Duplicate IATA Codes: Real Examples

BOS (historical): Boston’s Logan Airport uses BOS. Historically, a small airport in Bolivia also received BOS through an administrative error. The Bolivian airport eventually received a different code, but for years, careful context was required.

Regional versus international assignment: IATA code assignment involves coordination between regional offices. Occasionally, codes are assigned independently without cross-checking global databases. These duplicates typically surface quickly and are corrected, but they demonstrate that the system isn’t perfectly coordinated.

Active versus retired: Retired airport codes sometimes aren’t properly flagged in all systems. A new airport requesting a code might receive one that appears available but technically belongs to a closed facility. These conflicts require manual resolution.

How Airlines Handle Ambiguity

Reservation systems include more information than just the three-letter code, providing disambiguation even when codes overlap.

City codes: Airports associate with city codes that provide context. An ambiguous airport code plus a clear city code resolves to the correct location.

Full airport names: Ticketing systems display full airport names alongside codes. “BOS – Boston Logan International” is clearly different from any other BOS assignment.

Country codes: International systems include country information. Airports with the same three-letter code in different countries are distinguished by this additional field.

Pilot and ATC Systems

Flight operations systems have lower tolerance for ambiguity than passenger systems. Pilots and controllers need absolute clarity.

ICAO code preference: Flight plans use ICAO codes exclusively. The four-letter system with regional prefixes (K for U.S., C for Canada, E for Northern Europe) provides more unique combinations and clearer geographic identification.

Coordinate verification: Navigation systems include latitude/longitude coordinates for each airport. Even if codes somehow conflicted, coordinates provide absolute disambiguation.

NOTAM system: Notices to Air Missions reference airports by both code systems, full names, and coordinates. Pilots planning flights to any airport verify the correct destination through multiple data points.

Baggage Handling Challenges

Baggage systems present the highest practical risk from code duplication because routing decisions happen automatically based on code scans.

Bar code detail: Baggage tags include more than the three-letter code—flight numbers, dates, and carrier information all contribute to routing decisions. A bag tagged for “AA 123 to BOS” routes correctly because the flight number specifies the route.

Manual intervention: When ambiguity exists, baggage systems flag items for manual review. A code that appears in multiple contexts triggers human verification before routing.

Industry coordination: IATA coordinates baggage interlining standards that include disambiguation protocols. Airlines sharing baggage across connections use standardized formats that prevent misrouting.

Why Duplicates Still Happen

Historical legacy: Code assignment predates computerized global databases. Early codes were assigned regionally without real-time cross-checking. Some legacy duplicates persist in older records.

System limitations: With only 17,576 possible three-letter combinations and thousands of airports worldwide, the available code space is constrained. Pressure to find meaningful codes (matching airport or city names) increases conflict likelihood.

Private and military airports: Not all airports participate in commercial aviation systems. Private airstrips and military facilities may use codes that overlap with commercial assignments without creating operational conflicts.

Administrative errors: Human data entry errors occasionally create duplicates that must be caught and corrected. Quality control catches most before they propagate through systems.

Resolution Protocols

When duplicate codes are discovered, aviation authorities follow established procedures.

Priority assessment: Which airport has stronger historical claim to the code? Which has higher traffic? Which would be more disruptive to change?

Stakeholder consultation: Airlines serving affected airports, airport authorities, and national aviation agencies all participate in resolution discussions.

Transition planning: Code changes require updates across hundreds of systems. Transition periods allow parallel operation where both codes work while systems update.

Communication: NOTAMs, airline bulletins, and industry communications announce changes with sufficient lead time for operational preparation.

Near-Duplicates and Confusing Codes

Even without exact duplicates, similar codes create confusion risk.

Transposition errors: JKF instead of JFK, OAK versus OKA. Keyboard adjacency and mental transposition errors route passengers or cargo incorrectly.

Phonetic similarity: Codes that sound similar over radio create air traffic control challenges. DCA and DFW don’t look similar but can be confused in rapid verbal communication.

Training emphasis: Pilots and controllers train specifically on code verification. Reading back codes, spelling when ambiguous, and using full airport names all reduce confusion from similar codes.

The Metropolitan Area Complication

Large cities with multiple airports create special challenges because different airports serve the same destination.

Area codes: Some city pairs have area codes encompassing all regional airports. NYC includes JFK, LGA, and EWR. LON includes Heathrow, Gatwick, Stansted, Luton, and City Airport.

Passenger confusion: Travelers booking to “NYC” might not realize which specific airport they’re using until checking in. Different airlines prefer different airports, and connections between NYC airports require ground transportation.

System handling: Modern booking systems prompt travelers to select specific airports when area codes are entered. This prevents inadvertent booking to the wrong facility within a metropolitan area.

Future Code Capacity

Aviation growth continues adding airports worldwide while the three-letter system has fixed capacity.

Current utilization: Several thousand codes are assigned, leaving substantial unused capacity. But meaningful codes (those relating to location or airport names) are increasingly scarce.

Assignment creativity: New airports receive codes based on whatever combinations remain available. Some new codes have no obvious relationship to location—they’re simply unused combinations.

System evolution: Proposals exist for expanded code systems—four letters like ICAO, or alphanumeric combinations. Implementation would require massive industry coordination and system updates.

The Bottom Line

Duplicate codes are rare, quickly identified, and resolvable through the multiple redundant systems aviation employs. The parallel IATA/ICAO systems, combined with additional identifying information in operational databases, prevent the kind of confusion that could create safety issues.

For passengers, the practical risk is minimal—you’ll reach your intended destination. The systems designed for millions of annual flights have built-in safeguards that catch ambiguity before it causes problems. The rare duplicates that occur are curiosities of administrative process rather than operational hazards.