Canadian Airport Codes

It has to do with the transition from two-letter to three-letter codes.

Originally, airport codes were just two-letters. In Canada, they decided to use the same code as the Morse code for the corresponding Canadian railway station.

Eventually, it became important to know if an airport had a weather station on-site. Airports with a station prefixed “Y” to their two-letter abbreviation, for “yes.”

When the world switched from two-letter to three-letter codes in the 1930s, Canada simply retained the codes that had been established.