Whether you are looking for Sydney flights or US flights, many people tend to choose whatever airline offers the cheapest ticket or else the most convenient schedule. However there are quite a few people who, for one reason for another, have a preferred airline which they will always use where possible.
This can be for different reasons. Many business travellers have loyalty cards with their airline and they accumulate both points and air miles whenever they make a flight on that airline or one of its partner airlines.
This means that they get back free flights now and then and, if they travel often enough, they reach a certain status which means lots of extra perks such as use of the business class lounge even when travelling economy.
Other people choose certain airlines for safety reasons, even if it is only a perceived safety reason. Many people tend to think that their own national carrier is safer than many of the local airlines and fly with them whenever they can, although the actual safety figures might show differently.
Of course, having the luxury of being able to choose whichever airline you want is not always possible when it is a question of paying for your ticket yourself, but if you are travelling for business then it can be quite good fun to choose the flights and airlines that you want.