China is by far Australia’s largest trading partner. On the other hand the United States is China’s largest trading partner, with Australia quite behind on China’s list. Even though China is Australia’s number one trading partner, Australia is a free country, and an American ally, and therefore she supports the US on the issue of the South China Sea. China is trying to convert the South China Sea to a Chinese Sea. Actually that wouldn’t be good for Australia either.
China on the other hand threatens to down Australian aircrafts over South China Sea.
“China threatens to shoot down Australian surveillance aircraft over South China Sea”, December 2014