table of contents to seek an international solution through icao and that will allow the u.s . secretary of transportation to prohibit u.s . airlines from participating in the ets . ultimately , the scope and application of ets or other emissions trading schemes to our operations , now or in the near future , remains uncertain . similarly , within the u.s. , there is an increasing trend toward regulating ghg emissions directly under the caa . in response to a 2012 ruling by the u.s . court of appeals district of columbia circuit requiring the epa to make a final determination on whether aircraft ghg emissions cause or contribute to air pollution , which may reasonably be anticipated to endanger public health or welfare , the epa announced in september 2014 that it is in the process of making a determination regarding aircraft ghg emissions and anticipates proposing an endangerment finding by may 2015 . if the epa makes a positive endangerment finding , the epa is obligated under the caa to set ghg emission standards for aircraft . several states are also considering or have adopted initiatives to regulate emissions of ghgs , primarily through the planned development of ghg emissions inventories and/or regional ghg cap and trade programs . these regulatory efforts , both internationally and in the u.s . at the federal and state levels , are still developing , and we cannot yet determine what the final regulatory programs or their impact will be in the u.s. , the eu or in other areas in which we do business . depending on the scope of such regulation , certain of our facilities and operations may be subject to additional operating and other permit requirements , potentially resulting in increased operating costs . the environmental laws to which we are subject include those related to responsibility for potential soil and groundwater contamination . we are conducting investigation and remediation activities to address soil and groundwater conditions at several sites , including airports and maintenance bases . we anticipate that the ongoing costs of such activities will not have a material impact on our operations . in addition , we have been named as a potentially responsible party ( prp ) at certain superfund sites . our alleged volumetric contributions at such sites are relatively small in comparison to total contributions of all prps ; we anticipate that any future payments of costs at such sites will not have a material impact on our operations . future regulatory developments future regulatory developments and actions could affect operations and increase operating costs for the airline industry , including our airline subsidiaries . see part i , item 1a . risk factors 2013 201cif we are unable to obtain and maintain adequate facilities and infrastructure throughout our system and , at some airports , adequate slots , we may be unable to operate our existing flight schedule and to expand or change our route network in the future , which may have a material adverse impact on our operations , 201d 201cour business is subject to extensive government regulation , which may result in increases in our costs , disruptions to our operations , limits on our operating flexibility , reductions in the demand for air travel , and competitive disadvantages 201d and 201cwe are subject to many forms of environmental regulation and may incur substantial costs as a result 201d for additional information . employees and labor relations the airline business is labor intensive . in 2014 , salaries , wages and benefits were one of our largest expenses and represented approximately 25% ( 25 % ) of our operating expenses . the table below presents our approximate number of active full-time equivalent employees as of december 31 , 2014 . american us airways wholly-owned regional carriers total .
what percentage of approximate number of active full-time equivalent employees are passenger service personnel ?
.