United Continental Airlines ended 2011 as the world’s largest airline, overtaking Delta Air lines, according to the Center for Asia Pacific Aviation (CAPA).

American Airlines has dropped to third in the ranking, based on available seat kilometers, and through capacity cuts associated with its bankruptcy which may fall to fourth place next year, allowing Emirates to swoop in as third largest, said CAPA.

Emirates has moved into fourth place. Five US carriers feature on the top ten, while no mainland Chinese carrier is yet to be in the top flight although Hong Kong-based Cathay Pacific is in at number 10. China Southern is 12th, while Air China is 14th and could enter the top 10 in 2012 if cutbacks are enacted by Europe’s majors, including British Airways.

Other fast movers in 2011 have included Qatar Airways (20th) and Turkish Airways (23rd) and both are expected to keep climbing the rankings this new year, likely ending the year well inside the top 20, possibly at the expense of KLM and Air Canada, said CAPA.

The world’s airlines are scheduling 3.2% more flights this month, translating into 5.3% more seats and 7.3% more than in Dec. 2010.

With available seat kilometers growing faster than flights and seats, airlines are opening longer flights. Growth in this area is spurred by network carriers China Southern, Emirates, Etihad, Qatar and Turkish Airlines.

The largest mover in the top 25 low-cost carriers (LCCs) based on available seat kilometers was Volaris, the Mexican LCC that moved up six ranking positions and had the highest overall growth rate, 58%, of all of the top 25 LCCs.

Volaris has benefited from Mexicana’s 2010 exit and started rapidly increasing capacity in late first quarter of 2011. Volaris has now doubled its US presence while maintaining healthy load factors. Volaris is expanding out of Mexico City, a point it initially shunned, although smaller Mexican carrier InterJet has seen the largest overall growth.

Also making big moves in rankings were Air Berlin and Indigo, who each moved up two rankings. Air Berlin’s growth, however, has not been followed with profitability. Indigo is the largest carrier in India, which has the second-highest domestic growth rate after Chile, and is currently the only profitable one in the market.