pre_text: table of contents respect to the mainline american and the mainline us airways dispatchers , flight simulator engineers and flight crew training instructors , all of whom are now represented by the twu , a rival organization , the national association of airline professionals ( naap ) , filed single carrier applications seeking to represent those employees . the nmb will have to determine that a single transportation system exists and will certify a post-merger representative of the combined employee groups before the process for negotiating new jcbas can begin . the merger had no impact on the cbas that cover the employees of our wholly-owned subsidiary airlines which are not being merged ( envoy , piedmont and psa ) . for those employees , the rla provides that cbas do not expire , but instead become amendable as of a stated date . in 2014 , envoy pilots ratified a new 10 year collective bargaining agreement , piedmont pilots ratified a new 10 year collective bargaining agreement and piedmont flight attendants ratified a new five-year collective bargaining agreement . with the exception of the passenger service employees who are now engaged in traditional rla negotiations that are expected to result in a jcba and the us airways flight simulator engineers and flight crew training instructors , other union-represented american mainline employees are covered by agreements that are not currently amendable . until those agreements become amendable , negotiations for jcbas will be conducted outside the traditional rla bargaining process described above , and , in the meantime , no self-help will be permissible . the piedmont mechanics and stock clerks and the psa and piedmont dispatchers also have agreements that are now amendable and are engaged in traditional rla negotiations . none of the unions representing our employees presently may lawfully engage in concerted refusals to work , such as strikes , slow-downs , sick-outs or other similar activity , against us . nonetheless , there is a risk that disgruntled employees , either with or without union involvement , could engage in one or more concerted refusals to work that could individually or collectively harm the operation of our airline and impair our financial performance . for more discussion , see part i , item 1a . risk factors 2013 201cunion disputes , employee strikes and other labor-related disruptions may adversely affect our operations . 201d aircraft fuel our operations and financial results are significantly affected by the availability and price of jet fuel . based on our 2015 forecasted mainline and regional fuel consumption , we estimate that , as of december 31 , 2014 , a one cent per gallon increase in aviation fuel price would increase our 2015 annual fuel expense by $ 43 million . the following table shows annual aircraft fuel consumption and costs , including taxes , for our mainline operations for 2012 through 2014 ( gallons and aircraft fuel expense in millions ) . year gallons average price per gallon aircraft fuel expense percent of total mainline operating expenses .
post_text: ( a ) represents 201ccombined 201d financial data , which includes the financial results of american and us airways group each on a standalone basis . total combined fuel expenses for our wholly-owned and third-party regional carriers operating under capacity purchase agreements of american and us airways group , each on a standalone basis , were $ 2.0 billion , $ 2.1 billion and $ 2.1 billion for the years ended december 31 , 2014 , 2013 and 2012 , respectively. .
table: Year Gallons Average Price per Gallon Aircraft Fuel Expense Percent of Total Mainline Operating Expenses
table: 2014 3,644 $2.91 $10,592 33.2%
table: 2013 (a) 3,608 3.08 11,109 35.4
table: 2012 (a) 3,512 3.19 11,194 35.8
question: Analyse this data from a financial earnings document. what were total mainline operating expenses in 2013?