The CEO of the world's biggest airline says the new American Airlines Group Inc will be "a formidable competitor".
Doug Parker promised the carrier, formed from the merger of American Airlines and US Airways, will be better for both employees and passengers.
He said: "We are taking the best of both US Airways and American Airlines to create a formidable competitor, better positioned to deliver for all of our stakeholders.
"We look forward to integrating our companies quickly and efficiently so the significant benefits of the merger can be realized."
But he said the process will take time.
The airlines' separate websites, aa.com and usairways.com, as well as the two airlines' reservations systems and loyalty programs, will continue to operate separately until further in the integration process.
US Airways will exit Star Alliance on March 30, 2014 and will join the oneworld alliance the following day.
Customers will begin to see enhancements in early January, including the ability to earn and redeem miles when traveling on either American Airlines or US Airways, reciprocal American Admirals Club and US Airways Club benefits, and reciprocal elite recognition.
The airline issued a statement saying: "The completed merger also provides the path to improved compensation and benefits for employees.
"Alignment of pay, benefits, work rules and other guidelines for employees of both airlines will be phased in over time so that all changes can be carefully considered."
The merger was welcomed by the Association of Professional Flight Attendants, which represents cabin crew of American Airlines.
Union president Laura Glading said: "The flight attendants of the new American are looking forward to building the world's greatest airline."