The ADP expense section, like the revenue section, examines the system performance of each airline.

Since 2000, the components which comprise the total expense for each airline have undergone significant change.

There has been increased focus on labor costs, fuel, maintenance and the outsourcing of some services and departments. The ADP provides unit costs with each of these expenses either included or excluded. Furthermore, each relevant metric has been stage-length adjusted with the formula displayed.

The data-set concludes with a look at labor versus non-labor costs per available seat mile. The relationship between these two measures is a key factor as the industry enters labor negotiations for the first time following the industry-wide restructuring that occurred between 2001 and 2007.

In addition, we have calculated labor costs, excluding executive salaries, to provide insight on this key component of airline costs. While this measure is not perfect, it does help to put some context around this much publicized issue.

Again, all of the major items that go into calculating total expense are aligned, as reported to the DOT and the SEC. We encourage users to relate changes in expenses to changes in revenue.