WASHINGTON, Jan 24 (Reuters) - The Federal Aviation Administration said on Wednesday that airlines could begin returning grounded Boeing 737 MAX 9 planes to service once they undergo a thorough inspection and maintenance process after the agency halted flights on Jan. 6 following a mid-air emergency.

Separately, the FAA said it will not grant any production expansion of the MAX, including the 737-9 MAX. "We will not agree to any request from Boeing for an expansion in production or approve additional production lines for the 737 MAX until we are satisfied that the quality control issues uncovered during this process are resolved," FAA Administrator Mike Whitaker said in a statement. (Reporting by David Shepardson; Editing by Leslie Adler)