EVERETT, WA (MyBellinghamNow.com, AP) – Boeing says it will be several weeks before it fully resumes building passenger planes, as factory workers return following a nearly two-month long strike.

A Boeing spokesperson said on Nov. 12 that the delay in restarting plants in Washington and Oregon is due to multiple steps needed to resume production.

Airline customers have grown increasingly upset over delays in getting new planes from Boeing—delays that started long before 33,000 machinists went on strike on Sept. 13.

Boeing’s schedule for gaining certification of new 737 Max models has also been pushed back.

The strike shut down production of several passenger planes and cut deeply into Boeing’s revenue from delivering new planes. It comes as the company has announced plans to lay off roughly 10% of its workforce as early as this week.