Uncertainty around when Boeing’s 737 Max will return to service is leading key supplier Spirit AeroSystems to implement a voluntary layoff program for eligible employees. Monday’s announcement comes a little more than two weeks after the largest employer in Wichita said it would suspend production of the troubled aircraft’s fuselage, pylons, wing leading edges, thrust reversers, and nacelles.

“We do not know how long the pause in production will last, or what the production rate will be when it does resume,” Spirit said in a statement to AIN. “While no final decisions have been made on additional actions, we remain focused on doing what is in the long-term interests of Spirit, its stockholders and other stakeholders, including employees.”

The company’s biggest program, the 737NG/Max, accounted for 56 percent of Spirit’s $7.2 billion in net revenue in 2018. The tier I supplier employs about 12,500 workers at its Wichita headquarters.

Spirit carries out the manufacture of the 737’s fuselage in Wichita, while the company’s sites in Wichita and McAlester, Oklahoma, share responsibility for the other 737 components.