Sebring

From what I've read, that's even beyond the range of the 777-200LR models AC flies. The only aircraft that can fly YYZ-SYD nonstop is the 777-200LR in an all-passenger configuration, where most or all of the cargo space is converted to extra fuel tanks (a significant retrofit cost if you don't buy the planes from the factory like that). I'm not sure if any airline in the world has done that with the 200LR. It makes for an 18hour flight, which would mean a lot of extra crew cost. So no cargo, extra operating costs, etc. The route wouldn't be premium enough to make any money, and not prestige enough to justify the losses.