Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
|  |  | Year ended December 31, | Year ended December 31, | Year ended December 31, |
| --- | --- | --- | --- | --- |
|  |  | 2018 | 2017 | 2016 |
|  |  |  | As Recast | As Recast |
| OPERATING REVENUES: | Passenger | $20,455 | $19,763 | $19,068 |
| OPERATING REVENUES: | Freight | 175 | 173 | 171 |
| OPERATING REVENUES: | Other | 1,335 | 1,210 | 1,050 |
| OPERATING REVENUES: | Total operating revenues | 21,965 | 21,146 | 20,289 |
| OPERATING EXPENSES: | Salaries, wages, and benefits | 7,649 | 7,305 | 6,786 |
| OPERATING EXPENSES: | Fuel and oil | 4,616 | 4,076 | 3,801 |
| OPERATING EXPENSES: | Maintenance materials and repairs | 1,107 | 1,001 | 1,045 |
| OPERATING EXPENSES: | Landing fees and airport rentals | 1,334 | 1,292 | 1,211 |
| OPERATING EXPENSES: | Depreciation and amortization | 1,201 | 1,218 | 1,221 |
| OPERATING EXPENSES: | Other operating expenses | 2,852 | 2,847 | 2,703 |
| OPERATING EXPENSES: | Total operating expenses | 18,759 | 17,739 | 16,767 |
| OPERATING INCOME |  | 3,206 | 3,407 | 3,522 |
| OTHER EXPENSES (INCOME): | Interest expense | 131 | 114 | 122 |
| OTHER EXPENSES (INCOME): | Capitalized interest | (38) | (49) | (47) |
| OTHER EXPENSES (INCOME): | Interest income | (69) | (35) | (24) |
| OTHER EXPENSES (INCOME): | Other (gains) losses, net | 18 | 112 | 21 |
| OTHER EXPENSES (INCOME): | Total other expenses (income) | 42 | 142 | 72 |
| INCOME BEFORE INCOME TAXES |  | 3,164 | 3,265 | 3,450 |
| PROVISION (BENEFIT) FOR INCOME TAXES |  | 699 | (92) | 1,267 |
| NET INCOME |  | $2,465 | $3,357 | $2,183 |
Question:
In total how much was the operating expense incurred by Southwest Airlines in 2018?
Answer:
17,739