I recently located a newspaper report relating to a proposal for a combined International-Domestic Terminal at Sydney Airport along those seen today at Tullamarine Airport in Melbourne and Adelaide Airport.
It appears that the northwestern section of the airport had been selected as the site for the new terminal, where the new International Terminal would be built and opened in 1970.
Below is the article from The Daily Telegraph dated June 8 1965.
On the same page, there were also concerns over the development of the modern facilities at Sydney Airport and that Melbourne's new Tullarmarine Airport would be completed before Sydney Airport. Sydney Airport did open ahead of Tullarmarine airport in 1970.
It would have been interesting had the Federal Government gone for the combined terminal option, especially if extensions had to occur in the years ahead. The space where the International Terminal is located is tight as it is today. Imagine sharing it with the Domestic Terminal.
We could have ended up even with separate terminals for separate airlines as seen in numerous airports. Sydney Airport's layout would have made this challenging.
Interesting to note in the article of a possible rail link to where the Domestic Terminals are located today, which was to be linked to a future eastern suburbs railway line. The Airport Line (2000) would eventually see a station built there along with the international terminal. It linked the city, but instead of serving the eastern suburbs, it serves the western suburbs through a direct connection to the East Hills Railway Line.
And a need for two parallel runways. Only one of them became reality as reflected in the third runway (1994).