Singapore Airlines is a strong player in connecting flights from Europe or the US to the whole of Asia and Australia, and generally "Europe - Singapore - XXX" tickets are more profitable than purely "Europe - Singapore". Until the early 2000s, Singapore Airlines held an almost exclusive position on the so-called Kangaroo Route, the route from Europe to Australia that no transport aircraft can fly without a stopover. The company had built a strong position due to Singapore's geographical advantage, but with the arrival of Gulf airlines, this segment of Singapore Airlines has declined significantly.
Flights tend to be among the more expensive and it pays to book at least a month in advance.