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, | Year Ended December 31, | Year Ended December 31, |
| --- | --- | --- | --- | --- | --- | --- |
|  |  | 2019 | 2018 | 2017 | 2016 | 2015 |
| Select operating statistics (a) | Passengers (thousands) (b) | 162,443 | 158,330 | 148,067 | 143,177 | 140,369 |
| Select operating statistics (a) | Revenue passenger miles ("RPMs") (millions) (c) | 239,360 | 230,155 | 216,261 | 210,309 | 208,611 |
| Select operating statistics (a) | Available seat miles ("ASMs") (millions) (d) | 284,999 | 275,262 | 262,386 | 253,590 | 250,003 |
| Select operating statistics (a) | Cargo revenue ton miles (millions) (e) | 3,329 | 3,425 | 3,316 | 2,805 | 2,614 |
| Select operating statistics (a) | Passenger load factor (f) | 84.0% | 83.6% | 82.4% | 82.9% | 83.4% |
| Select operating statistics (a) | Passenger revenue per available seat mile ("PRASM") (cents) | 13.90 | 13.70 | 13.13 | 13.18 | 13.11 |
| Select operating statistics (a) | Total revenue per available seat mile ("TRASM") (cents) | 15.18 | 15.00 | 14.40 | 14.42 | 15.15 |
| Select operating statistics (a) | Average yield per revenue passenger mile ("Yield") (cents) (g) | 16.55 | 16.38 | 15.93 | 15.90 | 15.72 |
| Select operating statistics (a) | Cost per available seat mile ("CASM") (cents) | 13.67 | 13.83 | 13.02 | 12.70 | 13.08 |
| Select operating statistics (a) | Average price per gallon of fuel, including fuel taxes | $2.09 | $2.25 | $1.74 | $1.49 | $1.94 |
| Select operating statistics (a) | Fuel gallons consumed (millions) | 4,292 | 4,137 | 3,978 | 3,904 | 3,886 |
| Select operating statistics (a) | Average stage length (miles) (h) | 1,460 | 1,446 | 1,460 | 1,473 | 1,487 |
| Select operating statistics (a) | Average daily utilization of each mainline aircraft (hours:minutes) (i) | 10:39 | 10:45 | 10:27 | 10:06 | 10:24 |
Question:
What was the capacity of United Airlines in 2019?
Answer:
284,999