(Reuters) - Southwest Airlines plans to reduce service to and from Atlanta next year, affecting some employees on the impacted routes, unions covering the carrier's employees said on Wednesday.

The Southwest Airlines Pilots Association said the airline would schedule drawdowns from April next year and reduce the number of gates to 11 from 18.

The Transport Workers Union (TWU) Local 556, which represents Southwest Airlines' flight attendants, said that its members will retain their jobs. However, approximately 200 flight attendants will be asked to relocate.

The union also added that the airline's Atlanta base will remain open

"We continue to optimize our network to meet Customer demand, best utilize our fleet, and maximize revenue opportunities," Southwest said in a statement.

The news comes ahead of Southwest's investor day where the company is expected to update its annual and current quarter forecast.

The Dallas, Texas-headquartered airline is facing pressure from activist investor Elliott Investment Management, which is pushing for an executive shake-up and has reportedly communicated to one of the airline's top unions it wants to replace CEO Robert Jordan.

(Reporting by Nathan Gomes in Bengaluru and Rajesh Kumar Singh in Chicago; Editing by Tasim Zahid)