American Airlines Group Inc. will cull its management ranks as it sets a course to complete five years of work merging with US Airways.

“While not all integration work is complete, much of it is and as a result, now is the right time to look at the organizational structure we need for the future,” American Chief Executive Doug Parker and President Robert Isom wrote Tuesday in a memo to managers.

American did not say how many positions would be cut or give a financial target for cost savings. The airline has more than 12,000 positions that are considered management roles; Most of American’s 128,000 employees won’t be affected because the cuts don’t include jobs that involve customer interaction.

The deal combining American with US Airways closed in December 2013.

Much of the restructuring is expected to occur through attrition and by leaving vacant some of the 800 management positions that are now open, a spokesman for Fort Worth, Texas-based American said. Managers who have been at the company for at least two years have an option to accept a voluntary exit package with severance benefits.

Re-evaluating Organization

“As all companies do from time to time, we need to evaluate our current organization with a goal to operate more productively,” Parker and Isom wrote. “This work starts at the top.”

Last year, American told investors it had identified $1 billion in costs that it would trim by 2021, including “post-merger redundancies.”

The airline has only a few large items remaining on its merger to-do list. On Oct. 1, American will integrate its 26,000 flight attendants into a single system, allowing the company more flexibility with schedules and crew bases. That process was delayed by more than a year because of what American cited as the complexity of the task. The carrier also needs to mesh its dual aircraft-maintenance systems and its engineering and technology planning functions—a two-year process that’s expected to begin in 2019.

Last month, American cut its earnings forecast for 2018 because of a jump in fuel prices. U.S. airlines are also seeking to trim their non-fuel expenses due to a run-up in costs, mainly caused by more generous labor contracts negotiated after an era of bankruptcy.

American shares have declined by 20 percent this year, compared to an 11 percent drop on the S&P index of major U.S. airlines.