.s . and foreign carriers have entered into marketing relationships , alliances , cooperation agreements and jbas to exchange traffic between each other 2019s flights and route networks . see 201cticket distribution and marketing agreements 201d above for further discussion . employees and labor relations the airline business is labor intensive . in 2016 , mainline and regional salaries , wages and benefits were our largest expense and represented approximately 35% ( 35 % ) of our total operating expenses