American Airlines

The world's largest airlines can be defined in several ways. American Airlines Group is the largest by its fleet size, revenue, profit, passengers carried and revenue passenger mile. Delta Air Lines is the largest by assets value and market capitalization. Lufthansa Group is the largest by the number of employees, FedEx Express by freight tonne-kilometers, Ryanair by the number of international passengers carried and Turkish Airlines by the number of countries served.

By fleet size

Rank Airline Fleet (December 2013)

1 American Airlines 1,494

2 Delta Air Lines 1,280

3 United Airlines 1,264

4 Southwest Airlines 683

More Info: en.wikipedia.org