I can explain the "Y", but the "YZ" in the code for Toronto's Pearson Airport still has me a bit puzzled.
The international three-letter naming system arose in the 1930s when air travel (forgive the pun) took off. The system was a good short-hand reference for the world's airports, and with 17,576 possible combinations, there was no immediate risk of running out of codes.
Most airports adopted codes that, basically, made sense. They're either abbreviations for the city (SGN
for Saigon/Ho Chi Minh City) or for the name of the airport (JFK
, as you mentioned). Sometimes newer or more obscure airports have arbitrary codes, but for most of them there's at least a shred of logic.
Then we come to Canada. When airport codes were being handed out, certain groups lobbied successfully to reserve initial letters. The U.S. Navy laid claim to all the new "N" codes, "W" and "K" codes were reserved for radio stations, "Q" was reserved for international telecommunications. And Canadian aviation authorities said, "We want some uniformity in our airport codes. Give us a letter we can have all to ourselves." The letter chosen was "Y." So now almost all of Canada's airports have codes beginning with "Y," and almost all of the codes beginning with "Y" are for Canadian airports.
So if we know the codes have to start with Y, these make perfect sense:
: Montreal (Mirabel)
: Quebec City
YTX: Toronto (Island)
And these are reasonable if you squint a little:
: Calgary International
: Edmonton International
But then that brings us to YUL
- Montreal (Dorval) and YYZ
- Toronto (Pearson). I have not been able to find explanations for these. It's possible that Dorval had a previous name utilizing the "U" and the "L," though I haven't been able to find anything to support that. I'll make an educated guess and say that the second "Y" in Pearson's code stands for "York" and the "Z" stands for "nothing." It's entirely possible that both of these codes are simply random. Does anyone out there know the real story?
There are also several other a.net threads on this topic available at search, though no one seems to have the absolutely definitive answer.