that data is available here.
http://www.airlinefinancials.com/uploads/2013_Network_Annual_Summary2.pdf
in fact, DL spends a higher percentage of revenue on salaries and benefits than AA or US for 2013, the most recent data available.
note that DL has the highest average wage/salary per employee as well as the highest benefit cost per employee.
As a percent of revenue, UA spends more than DL because UA doesn't deliver the kind of revenue that DL generates.
but note also that DL generates more revenue per employee and more ASMs per employee than any of the other network carriers.
DL also has the lowest percentage of fuel cost AS WELL AS debt service compared to revenue
The simple reality is that DL does not scrimp on salaries but in fact pays its employees well and cuts costs elsewhere in order to keep its employees well paid.
IN turn, DL employees deliver above average revenue generation and above average productivity.
DL emploeyes are well compensated relative to their peers but they use their advantage to help the company succeed at its goals.
It is not a strategy that is much different from what WN does.
yet so many people here think it is a good strategy for WN to use because they are unionized but it isn't good because DL is largely non-union.