Why do airlines make use of break-even analysis ? Are there any characteristics of these companies, their operations and cost structures which can explain this?

1. Why do airlines make use of break-even analysis ? Are there any characteristics of these companies, their operations and cost structures which can explain this?
2. Would the analysis of load airline factors be different for a budget airline compared with a traditional airline which is not competing based on prices?
3.please add a question to continue a topic