Boeing told employees Monday that it will reassign about 3,000 workers who produce the 737 Max in the Seattle area, while a major supplier for the beleaguered jets said it is considering voluntary layoffs to cut costs as the grounding wears on longer than expected.

Boeing last month said it would shut down production of the planes in the middle of January, a drastic step as regulators reiterate they have no timeline to lift the flight ban on the planes, which they issued after two crashes in a span of five months killed 346 people.

Once the last plane currently in production is complete, Boeing told employees "no further [737 Max] airplanes will be produced until the suspension is lifted." Some workers will be moved to other programs like the 767 or 777X lines, while others will be assigned to storage facilities in Moses Lake, Wash. and a new site in Victorville, Calif.

"Hundreds of our colleagues from Everett came down to Renton in 2018 to help us during our production challenges. This gives the 737 team a chance to return the favor," Mark Jenks, vice president and general manager of the 737 program said in the note to employees, referring to a period when Boeing couldn't keep up with demand for the planes, its best-selling aircraft.

Spirit Aerosystems, which makes fuselages for the planes said it was considering voluntary layoffs and other measures to cut costs during the grounding, one of the most severe measures yet as the grounding hurts Boeing's vast 737 Max supply chain.

It isn't clear when regulators will approve the planes. Boeing has updated flight-control software that was implicated in both crashes but other concerns have emerged, such as how pilots can quickly react to malfunctions and subsequent alerts.

Boeing and the FAA said Sunday that they are evaluating whether wiring bundles on the 737 Max are too close together and pose a safety risk, a potential issue that was flagged in an internal Boeing audit, though the company said it was too early to tell whether design changes were needed.

Boeing said it would use the down time to improve quality at the Renton plant. The FAA last month said it was investigating production there after a former employee raised concerns about the impact on quality and workers due to the breakneck production pace.

"No decision has been made on when 737 production will restart due to the uncertainty about the timing and conditions of return-to-service and global-training approvals," Boeing told workers. "Once there is a decision, loaned employees will start returning to their regular assignments in a phased approach."