The first authorized delivery of mail by air in Canada was a flight in a Curtiss JN-4 (Canuck) biplane from Montreal to Toronto in 1918. Toronto’s importance as an air mail centre evolved over the next fifty years. The limited flying ranges of the early aircraft restricted most early mail flights to the Quebec City - Windsor corridor. Until the Second World War, international flights were limited to routes through Montreal, Buffalo and Detroit. The introduction of long-range jet aircraft resulted in Toronto becoming the leading air mail centre in Canada.

The early flights, while important to prove that mail could be carried by air, did not result in permanent air mail routes being established. The period from 1928 to 1932 saw the establishment of regular air mail routes. Mail was initially flown from/to Leaside Airport (closed in 1931), Downsview Airport (opened in June 1931), or Toronto Harbour (seaplane port). In 1932, the Department of National Defence raised concerns about winter conditions at the Downsview Airport and considered warning American and Canadian pilots to avoid Toronto during winter months.

Most of the early mail routes were short-lived and were closed down by 1932 due to the lack of funds during the Great Depression. The Downsview airfield was allowed to stay open as Toronto was developing as a major air mail centre within Canada.

The air mail routes were slowly re-established in the mid to late 1930's. On August 29th, 1938, the Toronto Municipal (Malton) Airport commenced operations as a major air mail centre and principal customs point of entry for aircraft from the United States.

Development of long-range aircraft during the Second World War improved mail services to and from Toronto. In 1941, the Post Office introduced special cancelling hammers for air mail through the Toronto airport.

The period between 1946 and 1958 saw significant improvements to commercial aircraft including longer flying ranges and turbo-prop engines. These advances meant longer air mail routes could be established through Toronto.

The first air mail to be carried by jet aircraft from Canada was on April 18th, 1950 on a test flight from Toronto to New York. However, it took until 1959 before regular air mail service by jet aircraft was established. By 1967 eight airlines were using Toronto International Airport (Malton). Jet aircraft have ensured Toronto’s position as the major air mail centre for Canada.

The presentation has been divided into periods of development. These are:

1918 to 1927 - Pioneer Years (frame 1)
1928 to 1932 - Beginning of Regular Air Mail Routes (frames 1 - 3)
1933 to 1937 - International Air Mail (frame 3)
1938 to 1939 - Air Mail Routes (frame 4)
1940 to 1945 - The War Years (frames 4 - 5)
1946 to 1966 - Air Mail Routes and Jet Age (frame 6)

Within each grouping, except for the Pioneer Years and 1933 to 1937- International Air Mail, the following sub-groupings have been used:

- Canada Air Mail Routes
- Canada - United States Air Mail Services and Routes
- International Destinations