IATA vs ICAO airline codes: Air India's boarding pass says AI. Its flight plan says AIC. IndiGo's ticket says 6E, but the strip an air traffic controller reads says IGO. Neither one is a typo, and neither one is wrong. They are two separate, official code systems, run by two separate organisations, and every scheduled airline in the world carries both at once.
Two organisations, two codes, one airline
The two-character code is assigned by IATA, the International Air Transport Association, the airline industry's own trade body. The three-letter code is assigned by ICAO, the International Civil Aviation Organization, the United Nations agency that sets technical standards for civil aviation. IATA's own code-search tool describes its two-character codes as identifying "an airline for commercial purposes in reservations, timetables, tickets, tariffs, air waybills and in telecommunications" (IATA, "Airline and Airport Codes Search," captured 2026-09-23). ICAO's three-letter designator exists for a different audience entirely: air traffic control, flight-plan filing, and other official aeronautical paperwork, per the same standards history recorded on Wikipedia's "Airline codes" page (captured 2026-09-23).
So the short version: same airline, same flight, two codes, because the two codes were built for two different jobs.
Why there are two systems at all
Both organisations actually started from the same code. ICAO issued two-letter airline identification codes from 1947, and for decades a single two-letter code did double duty: IATA adopted the same codes for its own commercial use, so one code covered the technical and commercial sides at once (Wikipedia, "Airline codes," captured 2026-09-23). That changed in 1982, when ICAO introduced its own three-letter designator system as the technical standard, which became official by November
- IATA did not switch over. It kept the shorter two-character format that airlines, travel
extended it once the pool of two-letter combinations started running out, by allowing a letter paired with a digit (Wikipedia, "Airline codes," captured 2026-09-23). That is exactly why IndiGo is 6E and not two letters: by the time IndiGo needed a code, the neat two-letter combinations were long since claimed, so it got a digit-plus-letter code instead.
The result, decades later, is two parallel numbering systems that never merged, because neither side had a reason to give up its own.
Where you actually see each one
You almost never see the ICAO code as a passenger, and that is by design. IATA codes are the ones built into every consumer-facing system: the two letters in front of your flight number on the ticket, the code the departure board uses, the code a travel search engine asks you to type in. ICAO codes live one layer down, in flight plans, in the strips and displays air traffic controllers work from, and in official aeronautical telecommunications (IATA, "Airline and Airport Codes Search," captured 2026-09-23).
There is a third identifier worth knowing, precisely because it gets confused with the other two: the radio call sign. A call sign is not a code you read off a screen, it is what a pilot actually says over the radio, and it is built from the airline's ICAO-linked telephony designator followed by the flight number, spoken aloud (Wikipedia, "Airline codes," captured 2026-09-23). So Air India's flight might be filed and controlled as AIC, but the pilot calls in as "Air India" plus the flight number, not by reading out three letters. Three different representations of the same flight, three different audiences.
India-first: Air India and IndiGo
Air India carries the IATA code AI and the ICAO code AIC. You will see AI on the ticket, the boarding pass and the departure board; AIC belongs to the flight plan and to air traffic control, not to anything a passenger reads. See the Air India directory page for the airline's code reference.
IndiGo carries the IATA code 6E and the ICAO code IGO. The 6E prefix is the one printed on every IndiGo boarding pass and quoted in every flight number you will ever book; IGO is the technical designator behind the scenes. See the IndiGo directory page for the same reference.
Neither pairing is arbitrary trivia. It is the reason a flight number search engine, a ticketing system and an air traffic control strip can all be talking about the identical aircraft while displaying three different-looking labels.
A few more, for contrast
The same two-code pattern holds everywhere, not just in India. Emirates flies as EK on your ticket and UAE to air traffic control. Qatar Airways is QR commercially and QTR technically. Lufthansa is LH on the boarding pass and DLH on the flight plan. In every one of these pairs, the two-letter or letter-digit code is the consumer-facing IATA designator, and the three-letter code is the ICAO designator built for aviation's technical side, not for you.
Why a boarding pass and a tracker can disagree on the prefix
This is the moment most people actually run into the two-code system: a boarding pass shows one prefix, and something else, a live map, an air traffic control feed screenshot shared online, or an aviation enthusiast's post, shows a different one for what is clearly the same flight. Nothing has gone wrong. The boarding pass is using the IATA code because that is what commercial systems were built around. The other source, if it is drawing from air traffic data, is often showing the ICAO-linked designator instead, because that is the identifier air traffic control actually works with. Once you know both codes exist for the same airline, on purpose, the mismatch stops looking like an error and starts looking like exactly what it is: two vocabularies for the same thing.
How TrackMyWings helps
TrackMyWings™ is a live flight-tracking platform in development, India-first in go-to-market with worldwide coverage. A private beta shipped on 2026-08-24: Android only, on the Play internal testing track, with a small group of named testers. The wider product, including a live map and trip management for the people waiting on someone's flight, is planned for launch rather than available today, and public launch has no fixed date. Our airline directory pages already carry the IATA and ICAO code pairs for airlines like IndiGo, Emirates, Qatar Airways and Lufthansa, a quick reference if a flight number or a code you spotted somewhere has you double-checking who actually operates it, while the wider tracking build continues.
Questions people ask
Why does an airline have two different codes? Because two separate organisations assign them for two separate purposes: IATA's two-character code is built for commercial use (tickets, timetables, reservations), and ICAO's three-letter code is built for technical use (air traffic control, flight plans).
Which code is on my boarding pass? The IATA code. It is the two letters, or letter-and-digit combination, in front of your flight number on the ticket and the departure board.
What is a call sign, and is it the same as an airline code? No. A call sign is spoken over the radio, built from the airline's telephony designator (linked to its ICAO code) followed by the flight number. It is how a pilot identifies the flight verbally, not a code printed anywhere on a ticket.
Why does IndiGo have a digit in its code instead of just two letters? Because by the time IndiGo needed a designator, most two-letter combinations were already taken. IATA extended its system to allow a letter paired with a digit, which is how IndiGo became 6E.
If I see a three-letter code for a flight, does that mean it's not a real airline code? It is real, it is just the other system. A three-letter code is almost always the ICAO designator, the one used in flight plans and air traffic control rather than on consumer tickets.
Sources
- IATA, "Airline and Airport Codes Search": https://www.iata.org/en/publications/directories/code-search/, captured 2026-09-23
- Wikipedia, "Airline codes": https://en.wikipedia.org/wiki/Airline_codes, captured 2026-09-23
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