YZ was the code for the station in Malton, Ontario, where Pearson Airport is located and hence the IATA code for Pearson Airport is YYZ. The telegraph station in Toronto itself was coded TZ, which is why Toronto's smaller Billy Bishop Airport is coded YTZ.

The difference between YYZ (Toronto Pearson International Airport) and YTZ (Billy Bishop Toronto City Airport) centers on scale and location. YYZ is Canada's largest and busiest airport, located about 25km (15 miles) northwest of downtown Toronto. It is the primary hub for international long-haul flights from Europe, Asia, and South America, and features two massive terminals with extensive lounges, duty-free shops, and high-frequency train links (UP Express) to the city center. YTZ, conversely, is a small "island" airport located directly on the edge of Lake Ontario in downtown Toronto. It is almost exclusively used for short-haul regional travel within Canada and the Northeastern U.S. (e.g., Montreal, Ottawa, Newark, Chicago) and primarily serves Porter Airlines. The "selling point" of YTZ is its extreme convenience; you can walk to your downtown hotel from the terminal via an underground pedestrian tunnel or take a 90-second ferry. While YYZ offers more flight options and lower prices for long distances, YTZ provides a "scenic," "boutique" experience with significantly shorter security lines and a much faster "curb-to-gate" time for business travelers.