Once completely combined, United became the world's largest airline, as measured by revenue passenger miles.

[6] UAH has major operations at Chicago–O'Hare, Denver, Guam, Houston–Intercontinental, Los Angeles, New York/Newark, San Francisco, and Washington–Dulles.

Additionally, UAH's United is the largest U.S. carrier to the People's Republic of China and maintains a large operation throughout Asia.

[9] Early in February 2008, UAL Corporation and Continental Airlines began advanced stages of merger negotiations and were expected to announce their decision in the immediate aftermath of a definitive merger agreement between rival Delta Air Lines and Northwest Airlines.

[11] Despite ending merger talks, Continental announced that it would join United in the Star Alliance.

The alliance is an agreement to link international networks and share technology and passenger perks.

The alliance took effect about a year after Delta Air Lines and Northwest Airlines completed their merger, as that released Continental from the SkyTeam contract and allowed for the required nine-month notice.

[14] United Airlines was reported to be in serious merger discussion with US Airways in early April 2010.

[17] Both airlines have taken losses in the recession and expect the merger to generate savings of more than $1 billion a year.

[18] Combined, they fly to some 370 destinations in 59 countries from their ten hubs,[19] and carry 144 million passengers a year.