Parent American Airlines Group Inc (>> American Airlines Group Inc), formed by the two airlines' 2013 merger, said that as early as July it will transfer about 10 percent of reservations booked on US Airways to American's existing reservations platform. The move will set in motion a transfer of the remaining US Airways reservations to American over some 90 days, the company said.

Travelers who seek to book on the US Airways website in the fall, after the 90 days are up, will be redirected to American's existing site, aa.com. Customers already ticketed on US Airways for July and beyond will receive an email with a new, American-only flight code.

For the airline, the transfer means extensive training for 9,000 US Airways airport employees and another 2,000 reservations agents to make sure they are comfortable with the new platform. It also means dealing with technical glitches should they arise, which could lead to flight delays and jammed phone lines.

Maya Leibman, American's chief information officer, told reporters that the potentially "hairy process" is "one of the most visible integration activities that an airline does in the course of the merger."

She said the company has curbed risk by limiting "the number of big changes that will happen at the same time on the same day."

American already joined its frequent flyer program with US Airways' earlier this spring.

By contrast competitor United Continental Holdings Inc (>> United Continental Holdings Inc) flipped the switch on both reservations and frequent flyer systems in a single day, which led to customer service delays.

The shift will mean that US Airways reservations will move to American's system, run by Sabre Corp (>> Sabre Corp) from a Hewlett-Packard Co-run (>> Hewlett-Packard Company) platform.

The timeline fits within the company's earlier pledge to complete the migration this year.

To finish integrating the two airlines, American must reach joint collective bargaining agreements with several more work groups and combine technical systems related to flight movement and dispatch.

(Reporting By Jeffrey Dastin in New York; Editing by Christian Plumb)

By Jeffrey Dastin