For example, an aircraft with 300 seats available for sale flying 1,000 statute miles would generate 300,000 ASMs for that particular flight.A lower CASM means that it is easier for the airline to make a profit, as they have to charge less to break even.For a simple example of the calculation of CASM, in the second quarter of 2011, Southwest Airlines (including its AirTran Airways subsidiary) had operating costs of $3.929 bn and 31.457 bn ASMs, as reflected in Southwest's SEC Form 10-Q for that period.Therefore, management's success at controlling costs is often judged by looking at how the airline's ex-fuel CASM changes from one period to another.For instance, in the second quarter of 2011 Southwest Airlines had fuel costs of $1.527 billion (again, including its AirTran subsidiary).In theory, the higher the RASM the more profitable the airline should be, assuming that the CASM remains constant.
