the following table shows annual aircraft fuel consumption and costs , including taxes , for our mainline and regional operations for 2018 , 2017 and 2016 ( gallons and aircraft fuel expense in millions ) . year gallons average price per gallon aircraft fuel expense percent of total operating expenses .

gallons: 2018: 4447
2017: 4352
2016: 4347
average priceper gallon: 2018: 2.23
2017: 1.73
2016: 1.42
aircraft fuelexpense: 2018: 9896
2017: 7510
2016: 6180
percent of totaloperating expenses: 2018: -23.6
2017: -19.6
2016: -17.6

as of december 31 , 2018 , we did not have any fuel hedging contracts outstanding to hedge our fuel consumption . as such , and assuming we do not enter into any future transactions to hedge our fuel consumption , we will continue to be fully exposed to fluctuations in fuel prices . our current policy is not to enter into transactions to hedge our fuel consumption , although we review that policy from time to time based on market conditions and other factors . fuel prices have fluctuated substantially over the past several years . we cannot predict the future availability , price volatility or cost of aircraft fuel . natural disasters ( including hurricanes or similar events in the u.s . southeast and on the gulf coast where a significant portion of domestic refining capacity is located ) , political disruptions or wars involving oil-producing countries , economic sanctions imposed against oil-producing countries or specific industry participants , changes in fuel-related governmental policy , the strength of the u.s . dollar against foreign currencies , changes in the cost to transport or store petroleum products , changes in access to petroleum product pipelines and terminals , speculation in the energy futures markets , changes in aircraft fuel production capacity , environmental concerns and other unpredictable events may result in fuel supply shortages , distribution challenges , additional fuel price volatility and cost increases in the future . see part i , item 1a . risk factors 2013 201cour business is very dependent on the price and availability of aircraft fuel . continued periods of high volatility in fuel costs , increased fuel prices or significant disruptions in the supply of aircraft fuel could have a significant negative impact on our operating results and liquidity . 201d seasonality and other factors due to the greater demand for air travel during the summer months , revenues in the airline industry in the second and third quarters of the year tend to be greater than revenues in the first and fourth quarters of the year . general economic conditions , fears of terrorism or war , fare initiatives , fluctuations in fuel prices , labor actions , weather , natural disasters , outbreaks of disease and other factors could impact this seasonal pattern . therefore , our quarterly results of operations are not necessarily indicative of operating results for the entire year , and historical operating results in a quarterly or annual period are not necessarily indicative of future operating results . domestic and global regulatory landscape general airlines are subject to extensive domestic and international regulatory requirements . domestically , the dot and the federal aviation administration ( faa ) exercise significant regulatory authority over air carriers . the dot , among other things , oversees domestic and international codeshare agreements , international route authorities , competition and consumer protection matters such as advertising , denied boarding compensation and baggage liability . the antitrust division of the department of justice ( doj ) , along with the dot in certain instances , have jurisdiction over airline antitrust matters. .

Questions:
what was the aircraft fuel expense in 2018 plus that in 2017?
what is the total sum including the expenses from 2016?

Answers:
17406
23586