<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by runningshoes:
Do the costs include only operating costs at flight levels, or do they include overhead associated with sales, marketing, maintenance, corporate structure, debt, and so on? Do the empty seats count or not? If they do then airlines flying at low seat yields look better by this measure than they really should.</font>
I believe that CASM and CPRM (cost per revenue mile - occupied seats) take into account ALL costs. Leaving out overhead wouldn't make for a very meaningful number.
What really matters, however, is whether the cash in is greater than the cash out - something lacking at almost every major US airline these days.
Revenue is measured against all seats and against purchased seats. So are costs. Thus, two numbers are generated, one representing yield for all seats and one representing yield for occupied (purchased) seats.