That information can all be gathered from companies' annual reports. Many can be found on the investor relations portion of thier websites, if not, they are public records and can be downloaded from many financial sites.
While most will not break the labor costs into employee groups, they will seperate the labor costs from the other expenses. I think you will find it quite illuminating to see the differences between the major carriers and the low cost carriers. It is pretty easy to see from where the lion's share of their cost savings is reached.
Good luck with the research.