There are several ways of defining the world's largest airline, and as such, several different airlines can claim the title at the same time.
By Scheduled Passengers Carried (Millions)
| Rank | Airline | 2012 | 2011 | 2010 | 2009 | |
|---|---|---|---|---|---|---|
| 1 |  Delta Air Lines | 164.6 | 163.8 | 162.6 | 161.1 | |
| 2 | United Airlines | 140.4 | 141.8 | 145.6 | 144.3 | |
| 3 | Southwest Airlines | 134.0 | 127.6 | 106.2 | 101.3 | |
| 4 | American Airlines | 107.8 | 107.2 | 105.2 | 104.5 | |
| 5 |  China Southern Airlines | 86.5 | 80.7 | 76.5 | 66.3 | |
| 6 | US Airways | 82.5 | 80.6 | 79.6 | 78.0 | |
| 7 |  Ryanair | 79.3 | 75.8 | 72.1 | 66.5 | |
| 8 |  Lufthansa | 74.7 | 65.5 | 58.9 | 55.6 | |
| 9 | China Eastern Airlines | 73.1 | 68.7 | 64.9 | 44.0 | |
| 10 | Air China | 72.4 | 69.7 | 60.0 | 41.3 |
Note:- Based on individual companies' published figures