Thousands of Boeing staff will get layoff notices within weeks, a union and industry sources said, as a senior U.S. official flew to Seattle to try to ease a crippling strike and a major airline issued a warning over the planemaker’s deepening turmoil.

Acting U.S. Labor Secretary Julie Su’s first in-person intervention comes days after Boeing unveiled plans to cut 17,000 jobs and take $5 billion in charges, continuing a year of tumult for the company.

Roughly 33,000 workers have been on strike since Sept. 13, seeking a 40% wage increase over four years.

Boeing will next month send out 60-day notices to thousands of workers including many in its commercial aviation division, meaning those staff will leave the company in mid-January, one source familiar with the matter said.

A second phase of notices, if needed, could be rolled out in December, the source said.