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, | Increase (Decrease) | % Increase (Decrease) |
| --- | --- | --- | --- | --- |
|  | 2017 | 2016 |  |  |
| Salaries and related costs | $10,436 | $10,034 | $402 | 4.0 % |
| Aircraft fuel and related taxes | 5,733 | 5,133 | 600 | 11.7 % |
| Regional carriers expense | 4,503 | 4,311 | 192 | 4.5 % |
| Depreciation and amortization | 2,235 | 1,902 | 333 | 17.5 % |
| Contracted services | 2,184 | 1,991 | 193 | 9.7 % |
| Aircraft maintenance materials and outside repairs | 1,992 | 1,823 | 169 | 9.3 % |
| Passenger commissions and other selling expenses | 1,787 | 1,710 | 77 | 4.5 % |
| Landing fees and other rents | 1,528 | 1,490 | 38 | 2.6 % |
| Passenger service | 1,067 | 907 | 160 | 17.6 % |
| Profit sharing | 1,065 | 1,115 | (50) | (4.5)% |
| Aircraft rent | 351 | 285 | 66 | 23.2 % |
| Other | 2,249 | 1,986 | 263 | 13.2 % |
| Total operating expense | $35,130 | $32,687 | $2,443 | 7.5 % |
Question:
how much revenue did Delta Airlines generate from Loyalty programs in 2016 ?
Answer:
2,184