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:
|  | Seats | Owned | Leased | Total | Average Age in Years |
| --- | --- | --- | --- | --- | --- |
| B737 Freighters | — | 3 | — | 3 | 17.5 |
| B737 NextGen | 124-181 | 141 | 10 | 151 | 7.5 |
| A319 | 119 | — | 10 | 10 | 10.2 |
| A320 | 146-149 | 10 | 43 | 53 | 7.3 |
| A321neo | 185 | — | 4 | 4 | 0.4 |
| Total Mainline Fleet |  | 154 | 67 | 221 | 7.6 |
| Q400 | 76 | 35 | 15 | 50 | 11.0 |
| E175 | 76 | 10 | 23 | 33 | 1.2 |
| Total Regional Fleet |  | 45 | 38 | 83 | 7.1 |
| Total |  | 199 | 105 | 304 | 7.4 |
Question:
How old were Alaska's aircraft in 2017?
Answer:
7.4