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In my flying experience (passenger), I've gotten used to seeing 3 letter airport codes. AKL = Auckland. LHR = London Heathrow. LGW = London Gatwick. LAX = Los Angeles. Generally, they seem to make sense - some sort of logic flow is applied to the name.

Which brings me to Canada. What bemuses me is when I see Canadian airports - they (so far) all seem to start with Y. YVR = Vancouver. YYZ = Toronto. YEG = Edmonton. And so on. VR is sort of an abbreviation for Vancouver, I guess, and Edmonton at least starts with an E, but I can't explain the Toronto one. And where the Y comes from I have no idea. Can anyone explain why they start with a Y, historically?

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    Many smaller airports in the US have little resemblance to the city name, too. One near me in Newton, Kansas is EWK. E and W are at least found in the city name, but K?!
    – Flimzy
    May 22, 2012 at 23:46
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    @Flimsy: nEWton, Kansas
    – Tor-Einar Jarnbjo
    May 23, 2012 at 16:09
  • For the second "Y" in "YYZ", I wonder if York (now a part of Toronto) is involved somehow... (I don't know if the airport is in former York or original Toronto.)
    – Monica Cellio
    May 25, 2012 at 19:27
  • @Flimzy The reason is that 'N' is reserved for Naval locations. See answer below.
    – Karlson
    May 31, 2012 at 13:29

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The short answer is that by regulation, the three-character IATA code for an airport in Canada generally corresponds to a three-character Transport Canada code (TCLID), which in turn generally corresponds to the last three letters of its four-character ICAO airport code. So why do the ICAO codes for Canadian airports all start with CY or CZ? That is murkier.

When the process of assigning international airport codes began during World War II, it integrated many existing identifiers set up by airlines, weather stations, radio navigation beacons, railway terminal telegraph stations, and so on. According to a quotation in an Airliners.net thread (take it for what you will, but it was the closest thing to a real citation I could find), Canada's were based on existing weather service codes:

Canada used two letters for identification of a weather reporting station. Additionally, preceding the 2-letter code, was placed a Y (meaning "yes") where the reporting station was co-located with an airport, a W (meaning "without") where the reporting station was not co-located with an airport, and a U where the reporting station was co-located with an NDB. An X was used if the last two letters of the code had already been taken by another Canadian ident, and a Z was used if the locator could be confused with a U.S. three letter ident. (section 2.18 pg 64)

I have also seen the theory advanced that the codes derive from radio transmitter identifers: ITU assigns the prefixes CF-CK, CY, and CZ to Canada, of which CY and CZ are reserved for transportation. CYYZ was the beacon at Malton, Ontario where Toronto Pearson International Airport is now located. On the other hand, airports like YQX and YYT have Canadian codes even though their corresponding radio callsigns would have had VA-VG or VO prefixes, the codes assigned for Newfoundland, which did not join Canada until 1949. It's possible that being closely tied to Canada, they used Canadian codes, or that they adopted new codes after confederation. It's also possible that some airports were designated after weather stations and others from radio transmitters, and that at least some transmitter codes are based on weather station codes in turn.

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I think that the best explanation for the Canadian Airport codes can be found in this article

Some special interest groups successfully lobbied the government to obtain their own special letters. The Navy saved all the new 'N' codes. Naval aviators learn to fly at NPA in Pensacola, Florida and then dream of going to "Top Gun" in Miramar, California (NKX). The Federal Communications Committee set aside the 'W' and 'K' codes for radio stations east and west of the Mississippi respectively. 'Q' was designated for international telecommunications. 'Z' was reserved for special uses. The Canadians made off with all the remaining 'Y codes which helps explain YUL for Montreal, YYC for Calgary, etc. (The start of the the song YYZ by the band Rush is the Morse code for the letters Y Y Z. Rush is from Toronto.) One of the special uses for 'Z' is identifying locations in cyberspace. What am I talking about? Well, an example is ZCX the computer address of the FAA's air traffic control headquarters central flow control facility. ZCX is not an airport but a command center just outside Washington D.C., that controls the airline traffic into major terminals.

Toronto's Pearson is probably a special case where YTO designates all airports in GTA, YTZ have also been taken and I cannot say for sure why YMI was given to Minaki rather then Pearson since it's located in Mississauga but here we have it.

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    The article provides a good overview, but it is more an attempt to explain quirky assignments like ORD for "Chicago O'Hare" or "GEG" for "Spokane International," and glosses over many details, like how or why Canada would need to "reserve" international "Y" codes with the U.S. government, or that FAA designations do not necessarily correspond to IATA designations.
    – choster
    May 31, 2012 at 18:35
  • @choster I don't think this was reserved with US Government. I think this was reserved at IATA though the article doesn't specifically say so. As far as ORD and GEG is concerned one needs to look at individual history of an airport like "ORcharD Field" for Chicago and "GEiGer field" for Spokane. Pearson's for example doesn't offer such a history that's why I offered a possible guess at the bottom.
    – Karlson
    May 31, 2012 at 19:55
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The reason you see resemblance is because its an "old" airport. Originally, airports were called by the city name. Los Angeles airport was LA, San Francisco was SF, San Jose was SJ, etc. These are the IATA codes.

But, there're not enough 2-letter combinations for all the airports, and an additional letter was added. Thus, LA became LAX (LAA is an airport in Colorado), SF became SFO (SFA is an airport in Tunisia), San Jose became SJC etc. New airports didn't have enough combinations available to follow the convention. Chicago's Orchard Field Airport became ORD (only "O" has any resemblance).

San Jose, California is SJC. But what about San Jose in Philippines? It's SJI. And San Jose in Costa Rica? It's SJO.

Other conflicts also affect the coding: for example London Gatwick Airport is LGW, because LGA is taken by the New York City LaGuardia Airport (both have LGA acronyms).

Many countries systematize the coding internally, for example many newer Canadian airports start with Y, which makes them grouped in the lists of airports. Newer 4-letter ICAO codes (not to be confused with the IATA 3-letter codes, they are not the same) have first letter (or first two) to mark the country/region K for the US (so LAX becomes KLAX), C for Canada (so Toronto YYZ becomes CYYZ), E and L for Europe, EG for the UK (making LHR changed to EGLL), etc etc. Some retain the 3 letters in the 4 letters' coding (like LAX->KLAX), some don't (like LHR->EGLL).

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  • Honestly, I don't think that this was a very good answer. Since the majority of Canadian IATA airports codes start with Y (more than 80% and not only new ones), there is likely a reason for it and not just that they had to take some arbitrary, free code. Several references on the net indicate that the ICAO codes precedes the IATA codes.
    – Tor-Einar Jarnbjo
    May 23, 2012 at 16:08
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    @Tor-EinarJarnbjo I actually specifically addressed this, but you didn't seem to have read to the end. IATA was formed in 1945, ICAO was formed in 1947. If you have sources saying otherwise - they're wrong.
    – littleadv
    May 23, 2012 at 18:10
  • I would really appreciate the downvoters to comment
    – littleadv
    May 24, 2012 at 20:35
  • @littleadv The ICAO was established in 1944 and began work in 1945, but the agreement that formed it was not fully ratified until 1947 (see icao.int/publications/pages/doc7300.aspx ). Besides, before that there was the ICAN (1903-1945).
    – choster
    May 24, 2012 at 21:37
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    This answers why airports may have codes that do not reflect their names or locations, but not why Canadian airports all have IATA codes that start with Y or Z. Many Canadian airports date to the early days of commercial aviation, so it is neither novelty nor coincidence that they should share Y and Z codes.
    – choster
    May 24, 2012 at 21:43
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I hope this image, which I prepared some time ago, sheds some light on the topic... Canadian airport idents

Transcription:

Origin of the strange Canadian Airport Codes Have you ever wondered why Pearson Airport is YYZ instead of something more logical like TOR? Well in 1930, when the USA decided to hand out 2-letter codes to its airports, Canada was late for the show. By the time Canada started issuing codes in 1937, it was decided that it could have the scraps left over - codes starting with oddball letters like Q, X or Y. (VR, WG, OW & UL were assigned before that decision).

The list seen here is the original Trans-Canada airway completed in 1939. See the pattern in the 1st letter? New routes, such as Windsor - London - Toronto, kept this pattern (thus QG - XU - YZ). Eventually Canada ran out of codes, so V and Z were added (W, ZE, etc.) In 1950, when the USA switched to 3-letter idents, again Canada was an afterthought. It was given Y and Z for the 1st letters. Now QP Princeton become YQP, YZ Toronto became YYZ, etc. After this point, at least the last 2-letters of new codes could make more sense (YTS, YMM, etc.) So that's how Canada got its strange airport codes.

There's a table in the image I skipped transcribing because this site doesn't have table markup.

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    You should probably indicate the source for this. Also, text-as-image is not much appreciated for many reasons (not searchable, not readable by screen readers...).
    – jcaron
    Mar 30, 2019 at 22:52
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    It's my own created image. As a meteorologist, I've done a lot of personal research into the history of weather and aeronautical radio stations. I posted this image rather than text because I already had it handy and thought this thread might find it of interest.
    – William Hepburn
    Mar 30, 2019 at 23:00
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Not all Canadian airports start with Y, though most do and certainly all the big ones - eg Bathurst New Brunswick is ZBF - and there are airports outside Canada that start with Y (search for "(Y" on http://aircargotracking.skysthelimitsd.com/air-freight-news/international-airport-codes/ for tons.) Nobody seems to know why, but my theory is to help everyone know if they were discussing an airport on the opposite side of the border or not.

There are four letter codes for the airports also, and those start with C - eg CYYZ for Toronto - but everybody seems to drop the C unless maybe they're discussing weather stations or radio frequencies.

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    3-letters coding and 4-letters coding are different coding systems. One is for IATA and the other for ICAO. They're not the same, and the 3 letters is not "drop the first letter of the 4". See my answer for an example.
    – littleadv
    May 23, 2012 at 0:38
  • @littleadv I agree in general about the 3/4, but for Canadian airports there are essentially no exceptions: see airlineupdate.com/content_public/codes/airportcodes/… about 2 dozen in the country, and the only one I've heard of is Breslau, and that's because I lived there as a child.
    – Kate Gregory
    May 23, 2012 at 1:01
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    That is also true for the US airports, but that is coincidental. It doesn't mean that the codes are the same. These are two different sets of codes, used for different things, and have different items in them. ICAO codes don't only include airports, for example.
    – littleadv
    May 23, 2012 at 1:03
  • @littleadv IATA bases their codes on the ICAO codes unless doing so would cause conflict with other IATA codes
    – jwenting
    May 25, 2012 at 5:56
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    @jwenting really? Then how do you explain EGLL<->LHR (and similarly all the rest of European airports)? Canada and the US are the exception, not the rule (Australia may behave the same as they own the whole region, as well).
    – littleadv
    May 25, 2012 at 6:19

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