Delta's Now The Second-Largest US Carrier
Delta beat out United to claim its spot as the second-largest carrier in the US last year. While those two are fighting for silver, American Airlines is expected to reign king for US carriers — at least in terms of total revenue passenger miles, an industry measurement tool that multiplies the number of passengers by the distance flown. There are quite a few other metrics for comparison, such as earned revenue or total traffic, but the latest numbers put Delta ahead of United for last year.
In 2015, Delta had a total of 209.6 billion revenue passenger miles, surpassing United's 208.6 billion. American (including the now-defunct US Airways) hasn't released its numbers for 2015 yet, but with 204.7 billion revenue passenger miles as of the end of November, it's likely that AA won't be overthrown. Delta's continued expansion both at home and abroad, as well as the continuing struggle of the 2010 United-Continental merger are possible explanations for Delta's edge over United.
While travelers interested in the points and miles game might not be too keen on Delta and its constant changes and devaluations, it's hard to argue that the carrier doesn't have a good network of appealing flights for travelers. As United bolsters its customer service and seeks to grow its own route map (especially with new long-haul Dreamliner service), it's possible that the airline could reclaim the spot in 2016.