For now, Delta is world's largest.

[Hatu]

United Airlines has held the title of world’s largest airline, as measured by traffic and capacity, since it merged in late 2010 with Continental Airlines.

But with United’s traffic reports released Wednesday afternoon, it appears that Delta Air Lines has passed United in size.

In July 2012, mainline United flew 471.4 million more “revenue passenger miles” than mainline Delta. In July 2013, it trailed Delta by 191.3 million RPMs.

In capacity, United led Delta by 886.8 million available seat miles a year ago. In July 2013, Delta led by 195.6 million ASMs.

http://aviationblog.dallasnews.com/2013/08/whos-the-worlds-largest-airline-in-july-it-wasnt-united-airlines.html/

 

[700UW]

Dont worry, the new American Airlines will be the world's largest airline.

 

[Glenn Quagmire]

Mine is bigger than yours...

 

[WorldTraveler]

Given the different timelines for mergers, a truly apples to apples comparison can't predict where the industry will be. UA held the title but it didn't cut a lot of the capacity necessary to boost its RASM. Now that UA is cutting capacity to get RASM up, their relative position changes.

It is not certain where it will all shake out.

More significantly, it's not clear what the title of #1 really means when it comes to customer preference; earnings; or employee pay, benefits, and security with the latter probably most of interest to people on this forum.